Plate Tectonics Archives - Page 2 of 3 - Geodiversity Education Foundation

Two photos side by side showing a man standing beside large amethyst geodes. Text in front of the photos reads "Geoscience Today: Visit to Ametisto so Sul, Brazil"

Visit to Ametista do Sul, Brazil

Brazil has long been famous for its tremendous amethyst deposits. I recently checked off a major bucket list item by visiting Ametista do Sul, which is in the northern part of the state of Rio Grande do Sul in southwestern Brazil. This is the main area that produces Brazil’s famous amethyst geodes. Production is about 400 tonnes per month. These geodes occur in basaltic volcanic flows formed about 130 million years ago. Typically, geodes form in a spherical cap-shape, sometimes elongated vertically. The outer layer of the geode is made of celadonite, a dark green mineral in the mica family. This outer layer is very useful to miners looking for geodes, as the dark green celadonite is easily recognizable. Under the celadonite there is a layer of agate (chalcedony), then colourless quartz, then finally amethystine quartz. At Ametista do Sul, the geodes occur in a 40 to 50m thick basaltic lava flow that formed in the Lower Cretaceous period. When the lava formed, there were especially large gas bubbles trapped in the rock. Water entered the empty spaces through fractures, over time forming the amethyst geodes. First stop was at the Belvedere mine, which has a terrific underground tour including a demonstration of drilling with an old jackleg and an actual blast. They use black power, which is a low impact explosive (gunpowder), to just gently break the rock around the geodes, which are then carefully excavated by hand using chisels. When a geode is located, the miners make a small hole in it and then put a light inside to evaluate the quality of the amethyst. The value of the geode increases the darker the purple and the larger the crystals. Sizes of geodes are very variable but can be up to as much as 3 metres long. The mine has a magnificent display of amethyst geodes in their underground gallery, which you can see in the accompanying photos. These geodes are enormous – up to about 2 metres long by 1 metre wide. Several are accompanied by very beautiful carvings in basalt. Several geodes of citrine are also on display. Geodes with low quality colour are typically heated to form yellow citrine. This converts ferrous iron to oxidized ferric iron causing the colour change. The majority of citrine is formed by heating amethyst as it rarely occurs naturally. In addition to its mine tour and extensive gallery, the mine also has an underground wine bar where you can sample wines made in the area and pick up a bottle or two (which I did). This is also a remarkable underground restaurant at the Belvedere Hotel. Every table has an enormous geode in the middle of it covered by glass. You can also see some geodes in the wall of the mine and there are some fabulous geodes also on display. In addition, there is an underground pool and hot tub next to the restaurant for hotel guests to relax in. Clearly the hotel is doing very well as it has embarked on a major expansion to its facilities adding a series of cabins and a new major display area. After the marvellous mine tour and lunch, we then went into the centre of town to visit a huge rock and mineral store called LP Minerais (lpminerais.com.br) in downtown Ametista do Sul. I have never seen so much amethyst, agate, rock carvings, etc, in one place. It was spectacular. The back room was filled with more amethyst geodes waiting to be sold and shipped. I picked up some terrific samples to take home! This was an absolutely amazing day!! Dr. Bill Pearson, P.Geo. has over 40 years of experience in the national and international mining industry and has carried out exploration and development programs in 17 countries around the world. He is formerly Vice President, Exploration for Desert Sun Mining Corp. (prior to April 2006 takeover by Yamana Gold Inc.), Executive Vice President, Exploration for Central Sun (prior to April 2009 takeover by B2Gold Inc.) and is currently President & CEO of Coastal Gold Corp., a junior mining company whose principal project is in southwestern Newfoundland. Dr. Pearson is the recipient of the 2015 PDAC Distinguished Service Award for his service to Canada’s Mineral and Exploration Industry. He convened the first meeting of the Committee for the Professional Registration of Geoscientists of Ontario (CPRGO) in March 1989, which he chaired for seven years. He was President of the Association of Geoscientists of Ontario (AGO) from 1996 to 2000 and was the founding President of Professional Geoscientists Ontario (PGO) from 2000 to 2003. In addition to his work for the geoscience profession in Ontario, Dr. Pearson was instrumental in the formation of the Canadian Council of Professional Geoscientists (CCPG now Geoscientists Canada), where he served as one of CCPG’s founding directors. He is founder and Chair of the APGO Education Foundation.

Oasis in the Deep Sea: Hydrothermal Vents

The deep sea is so different from other ecosystems on Earth, it’s almost like another planet! In fact, the deep sea is so isolated and mysterious that we know more about the Moon than we do about the ocean floor. Deep-sea hydrothermal vents, also called “black smokers,” are areas along the seafloor that discharge scalding hot water. They are located near areas of high tectonic activity and volcanic sites, commonly near mid-ocean ridges (MORs). These black smokers are important because they host a variety of exotic organisms, can help us to understand hydrothermal processes along mid-ocean ridges, and have economic importance. In 1976, a series of temperature spikes were observed by scientists exploring a mid-ocean ridge near the Galapagos Rift. From this data, scientists discovered hydrothermal vents, along with new ecosystems and species within these vent systems. The vents were first observed through a seafloor imaging system, in which a camera is submerged in water to take photos of the observation target, and the images are used to create seafloor maps. The first direct observations occurred when a manned submersible, The Alvin, was used to observe and sample the vents and their ecosystems. There was great fascination with this discovery since up until this point scientists thought that life required sunlight to exist. But here there was a thriving ecosystem that found its own source of energy devoid of light. Black smokers are probably the last place you would expect to find life, since they spew toxic material and there is absolutely no light. These eerie vents, however, are home to complex ecosystems with a thriving community of biotic creatures. At the base of the food chain there are bacteria and Archaea, which produce energy through chemosynthesis. Chemosynthesis is a life-process where inorganic carbon is converted into carbohydrates using inorganic molecules. Chemosynthesis involves using energy released by inorganic chemical reactions to produce food. These inorganic reactions include inorganic compounds, such as hydrogen sulfide or hydrogen gas undergoing oxidation, acting as the energy source. Many kinds of chemosynthesis occur, as there are different kinds of bacteria that can oxidize substances varying from sulphur to methane, even iron, and manganese. This variety of bacteria form the base of a food chain that includes deep-sea clams, mussels, and giant tube worm species. These species live in symbiosis with the chemosynthetic bacteria and would not exist without this relationship. Viruses discovered in these environments interact with bacteria. Horizontal Gene Transfer (HGT) is a process in which a virus implants some of its DNA into a bacteria, reaping some of the bacteria’s DNA. Viruses have the power to alter the bacteria’s gene expression, giving the virus the unique ability to carry different kinds of genetic information, which is useful in such extreme environments. This allows the bacteria to survive in ever-changing environments. HGT occurs due to the number of bacteria and viruses suspended in these environments and is important to the species’ evolution. The type of vent, distance from the vent, and lifetime stage of the vent are all factors that dramatically change the temperature and mineral concentration of the region. For bacteria to survive, they need to be able to adapt relatively quickly to rapidly changing habitats. HGT allows the bacteria to survive in its new environment and produce versatile offspring. The geosphere, hydrosphere, and biosphere are the three main Earth systems that interact with hydrothermal vents. Since there is no sunlight for life processes in hydrothermal vent ecosystems, the energy required by living organisms is gained from tectonic movement near the MORs. Water seeps into the ridges, is heated by magma, then mixes with minerals. Fine-grained sulphide minerals containing metals such as copper, zinc, lead, gold, and silver from the Earth’s crust are dissolved in high concentrations in hot hydrothermal fluids. When these metal sulphides are exposed to cold ocean water, they form black chimney-like sulphide deposits around each vent, hence the name black smoker. The water that is ejected contains methane and sulphides; substances required for chemosynthesis. The nature of chemosynthesis illustrates how intertwined Earth’s systems are; the removal of the biosphere would nullify the existence of such a fascinating ecosystem. Hydrothermal vents contain exotic ecosystems threatened by the prospect of deep-sea mining. Deep-sea mining is becoming a popular consideration for mineral exploitation as the popularity of land mining is rapidly diminishing land-based ore deposits. Mineral ore deposits are composed of fine-grained sulphide minerals containing metals. Although deep-sea mining may benefit the economy due to the abundance of ore deposits, there is controversy about destroying these ecosystems. Some argue that mining near black smoker active volcanic sites is reasonable because the volcanoes will erupt across many square metres of the seafloor, causing destruction in these sites. Environmental advantages for deep-sea mining, as opposed to land-mining, results in no waste rock, no acid mine drainage, and no holes in the ground that could contribute to seismic activity. Deep-sea hydrothermal vents are vital to both marine ecosystems and mineral ore deposits for deep-sea mining. They contain ecosystems hosting many organisms using exotic life processes to create energy such as chemosynthesis, as well as hosting mineral ore deposits. These hydrothermal vent ecosystems are vital to the environment. Developing ecofriendly deep-sea mining technologies could be important for preserving deep-sea ecosystems. Kathryn Cheng is an undergraduate student at the University of Toronto, pursuing a B.Sc in Geology and Chemistry. She has an interest in hydrothermal vent systems and isotope geochemistry. She is currently conducting research in the Metal Isotope and Isotope Biochemistry Lab at UofT investigating mercury contamination from artisanal small-scale gold mining in South America. Kathryn is the President of the Undergraduate Earth Sciences Association at UofT and the Women in Mining UofT student chapter.

Scientific Ocean Drilling with the JOIDES Resolution: A summary

Have you ever wondered how scientists study the rocks and sand on the bottom of the ocean? The International Ocean Discovery Program (IODP) is a research program dedicated to investigating sediments and rocks at the bottom of the ocean as a way to understand the history and structure of the Earth as well as the processes that shape our planet. IODP is funded by the US National Science Foundation and by national research agencies in 25 countries around the world. To be able to do the research as planned they need a research vessel that has the capability to collect rock and sediment samples from deep in the ocean. One of those vessels is called the JOIDES Resolution (often called The JR; see photo below). The JR has an international crew of seafarers, drillers, scientists and engineers all with the goal of improving our understanding of how geology, oceans, life and the atmosphere interact on Earth and how these systems have evolved over millions of years. Scientific ocean drilling has been a highly successful international collaboration for more than 50 years. The first ocean drilling vessel, before the JR, was a famous ship, Glomar Challenger, that roamed the world’s oceans from the late 60’s until the early ‘80s and directly contributed to our understanding of tectonic plates and how they form (see maps below). Today, the JR conducts 4 to 5 expeditions every year collecting samples and data of oceanic crust and sediments from all over the oceans to continue to build a better understanding of our planet, both past and present. Below are some example questions that were asked when the JR and predecessors have gone out on research expeditions: How is the ocean crust formed at ocean ridges? How does the ocean crust react with seawater and change over time? What were climate and oceans like during different times in Earth’s past and can we learn about future climate change? How has life evolved in the oceans? If you can ask a question, they want to answer it. The JR is venturing out to sea yet again this year to complete the IODP Expedition 393, the final chapter of a four-year expedition research project called the South Atlantic Transect. The last time this transect was visited to this extent was with the Glomar Challenger back in the 1960’s. The sites run perpendicular to the western flank of the Mid Atlantic Ridge, a range of submarine mountains that runs down the middle of the Atlantic Ocean where new oceanic crust is made and moves laterally (to the side) as it cools and sinks. This allows many processes related to ocean crust formation and aging to be studied. The Expedition 393 science team includes an array of different science fields. For instance, the team includes geoscientists that will be studying the microscopic fossils that can be found preserved within the ocean sediment. Microscopic refers to a significantly small item that requires the use of a microscope to see it. The science team also includes microbiologists that study the microscopic living organisms that are in the sediment and rock of the ocean floor! This addition to the research will help us better understand the extent of life on our planet. You can read more about the South Atlantic Transect 2 and the expeditions that came before it on the blog of the JR. You can also partake in the adventure and join the Onboard Outreach Officer, Tessa Peixoto, virtually on Zoom for a free ship tour. Expedition 393 will happen between June 7 and August 7, 2022. Whilst on the tour you will have the chance to speak to the scientists on board and ask them questions of what it is like to do research at sea. Email thejoidesresolution@gmail.com to find out more about how to sign up! Sources: Earth’s tectonic plates, Image, Encyclopædia Britannica, Encyclopædia Britannica, https://www.britannica.com/science/plate-tectonics#/media/1/463912/172045, June 11, 2022 IODP – International Ocean Discovery Program IODP Canada The value of rocks.A poem by Tessa Peixoto What is a rock,If not shelter from a predator,Or weather.What is a rockIf not a solid place to attach one’s holdfast.What is a rock,If not a used to be skipped across a calm surface of water. A rock is just that.A shelter.An anchor.A form of entertainment. A rock is also a storyteller.Its parts,If you pay attention long enough are called elements.Its parts,are the keys to understanding history.History that tells of death, change, and renewal. So…What is a rock,If not the burial grounds of fallen foraminifera.What is a rock,If not filled with crystalline rivers of minerals.What is a rock,If not the sedimentary pages of a changing ocean. -Tessa Peixoto, the author of this article, is the Onboard Outreach Officer for Expedition 393. You can find her poem here and the JOIDES resolution blog here.

Aerial photo of Toronto with CN tower and skyscrapers. In front of photo text reads "Geoscience Today. Contrary to popular belief, Eastern Canada is more at risk of earthquakes than perceived."

Contrary to popular belief, Eastern Canada is more at risk of earthquakes than perceived

Author: Alexander Lewis Peace, Assistant Professor (Structural Geology), McMaster UniversityThis article is republished from The Conversation under a Creative Commons license. Read the original article here. Most Canadians believe that the greatest national risk of a devastating earthquake lies in British Columbia. The whole Pacific northwest coast, with its rugged topography and history of the San Francisco and Los Angeles earthquakes farther south, is what typically comes to mind when we talk about the “big one” that has yet to hit. We want to change that perception while there’s time. A closer look at the complex factors at play, both under and on the Earth’s surface, shows that some of the worst risk is actually where Canadians are probably least expecting it: in a zone running from the Great Lakes to the St. Lawrence River that includes major cities like Toronto, Hamilton, Ottawa, Montréal and Québec City. Experienced preparedness It’s true that the same faults that put California and parts of the West Coast of the United States at risk also make B.C. a serious earthquake concern. The notorious “Pacific Ring of Fire,” where massive tectonic plates are constantly threatening to reshape the landscape as they shift, collide and overlap, is aptly named. It’s safe to say coastal B.C. has a culture of earthquake readiness. People on the West Coast are much more aware and better prepared. They are familiar with emergency protocols, and many keep a survival kit handy in case a quick exit becomes necessary. Seismic monitoring is abundant, and far more buildings are designed or retrofitted to mitigate the potential for serious earthquake damage. This is not the case in southern Ontario and southwestern Québec, even though the risk is significant as more than half of Canada’s population lives in this vulnerable corridor. What is the source of this complacency? Understanding risk It likely has to do with the type of risk. In Eastern Canada, the threat is not directly from the interplay between plates of the Earth, as it is in the west. In Ontario and Québec, the risk is from the less sexy but still deadly intraplate activity — seismic activity that occurs in the middle of tectonic plates which are not directly associated with plate boundaries. Intraplate areas also have faults. Some, dating as far back as the formation of the continents, can be reactivated under certain stresses, such as when pressure on the edges of plates thousands of kilometres away push on them, causing them to move. Lines of weakness dating back millions of years can become hazardous once again when new stresses come into play. When the last of the glaciers receded about 11,000 years ago, for example, their massive weight left the Earth’s surface dented. That’s a long time to us, but it’s a snap of the fingers in geological time. In places where the ground has not yet “popped” back into place, it is overdue to do just that, potentially violently pushing people, buildings and infrastructure out of the way. Earthquakes happen all the time in Canada. There are about 4,000 every year, most of them too small or too remote to notice. But from time to time, there are much stronger quakes. A disproportionate number of those have happened in Eastern Canada, especially in the Ottawa Valley and western St. Lawrence Valley, in seismic zones that include Ottawa, Montréal and Québec City, but also farther west, in the highly populated seismic zones of the lower Great Lakes. We are not the first to suggest these hazards in Ontario and Québec need more attention, but our recent research confirms these risks are real and the threat is imminent. Reading the landscape In Canada, there isn’t a very long record of instrument-recorded seismological activity, especially in the eastern region, but we do have abundant physical evidence of significant earthquakes from the past, which still remains the best predictor of future events. The bottoms of major lakes in Ontario and Québec, for example, provide a significant and still visible record of sediment upheaval that could only have been caused by major earthquakes long before human settlement. As scientists we feel bound not to panic anyone unduly. At the same time, we feel a duty to offer warnings where they are needed, and this is certainly one of those instances. The risk in Eastern Canada has less to do with magnitude, which can be measured on the familiar Richter scale, and more with vulnerability. A lower magnitude quake that strikes in a vulnerable area, such as a densely populated city like Montréal, can still be catastrophic, especially if it happens at the wrong time of day, such as rush hour or in the middle of the night. Predicting the timing of earthquakes is still beyond the reach of science, and even if we knew precisely when and where a quake was coming, there would still be nothing we can do to stop it. What we can do is take action to mitigate harm from seismic events through infrastructure design, pinpointing more specific areas of heightened risk through research and making sure that resources, including insurance, are available for recovery. In Canada, most of the anticipation of big earthquakes focuses on the Pacific coast. We’d like everyone to add the Great Lakes and the western St. Lawrence region to that mental file — and to be ready. I am a structural geologist leading the McMaster Structural Geology and Tectonics Group, in the School of Earth, Environment and Society at McMaster University. I research deformation processes and associated hazards as well as resources. I am particularly interested in rifting and breakup, rift-related magmatism, seismic hazards, and structural inheritance. Geographically, I have worked around the North Atlantic, with a particular emphasis on Eastern Canada. The nature of my work requires a multifaceted approach incorporating a wide variety of approaches and methodologies such as: seismic interpretation, field-based studies, numerical modelling, petrology, structural modelling and geochemistry.

A Celebration of Kingston Geology

We at the APGO Education Foundation are always looking for an excuse to celebrate geology. What better way to do that than to sing the geological praises of the Kingston area! On Saturday, May 7, 2022, the APGO Education Foundation and Mining Matters will be hosting a table at the Science Rendezvous event in Kingston, Ontario, at the Leon’s Centre. We hope that you will drop by and talk a bit of shop with us, because we haven’t been able to talk about geology with you in person for so long! This year our theme is “The Geology of Kingston.” From May 7-22, we will be offering a geology themed scavenger hunt where you can earn your digital “Geo-Explorer Badge” of Kingston, and a chance to win one of five cool prizes. Choose from a list of geologically interesting rocks listed on our site, then visit a minimum of six of those rocks located either on Queen’s campus or along the Kingston Waterfront. Take an original photo of the rocks you visit, then submit them to us online. That’s it! If you have visited the correct rocks and submitted an original photo, then you will qualify to win one of five beautiful geology textbooks. Five winners will be randomly selected from qualifying entries. You can also visit us at our booth on May 7th to look at some rock samples of Kingston and talk about how they formed. Did you know that Kingston is also called the Limestone City? People used to build limestone buildings right on top of the limestone they excavated to make them! But limestone isn’t all that Kingston has to offer. Not even a little bit. To say that Kingston has a complicated past would be a big understatement. The area shows evidence of so many geologic events throughout the past billion-plus years that it requires a lot of detective work by geologists to try and piece these events together. Perhaps we’ll never know the full detailed story; however, we can be sure it will give geologists something to think about for centuries to come. To the northeast of Kingston lies a strip of Precambrian rock called the Frontenac Arch. It connects the Precambrian rocks of Algonquin Park to the northwest to those of the Adirondack Mountains to the southeast. The rocks themselves were formed between 1.1 to 1.4 billion years ago, the later stages of which were thought to be a time when there was quite a bit of volcanic activity, resulting in a lot of magma being deposited on the continent1. As if all this magma spewing all over the ground wasn’t enough excitement, the igneous rocks that formed from this magmatism were then deformed due to a process called metamorphism. This metamorphism was a result of an incredibly massive mountain-building event, or what geoscientists call “orogenesis”. This mountain building event is called the Grenville Orogeny, and it lasted until about 980 million years ago. The mountain range itself was massive – it ran from Labrador, Canada, down to Mexico, in a northeast to southwest direction. The mountains formed when at least two continental landmasses collided with Laurentia, the large North American continental landmass at the time. The term “collide” implies an immediate event. But the movement of continental plates is not instantaneous; average plate movement is 10 cm per year. While this rate of movement might seem inconsequential at first, remember that continents are ridiculously massive in size and just because they come in contact with another on-coming continent does not mean they stop moving! Once a continent collides with another continent head-on, the ground starts to buckle and has nowhere to go but up. Think about the last time you shoveled your driveway (brr!). When you put your shovel down, the snow is flat and beautiful, just as it was deposited. When you start to push your shovel though, the snow buckles and builds upwards, forming little mountain-like structures made of snow on your shovel. In orogenesis, instead of snow, the ground itself is pushed upward on a massive scale, forming mountains. Over many millions of years, the Grenville Orogeny was formed in North America, its western edge giving Kingston, Ontario a high five. You might be thinking “Wait, I’ve been to Kingston and there weren’t any mountains there!” You’re right… and you’re wrong. Like all good things, even mountains must come to an end. Once the continents stopped pushing into each other, the ground was no longer being pushed upwards and the mountain building phase ended. With no upward building, the mountainous sediments had nowhere to go but down. Over the next several hundred millions of years, the powerful effects of weathering and erosion wore the mountains down until not much remained but their roots. When you walk over the Frontenac Arch, you are walking on the roots of an ancient mountain! At one point in time, these very rocks were at the bottom of a mountain as tall as the Himalayan Mountains. With that amount of weight sitting on top of you, you can imagine things would get pretty uncomfortable. The rocks found in the roots of a mountain are commonly subjected to metamorphism. Because of the high temperatures and pressures there, they undergo deformation, which alters the original (or “parent”) rock to form a secondary, and ultimately, metamorphic rock. For example, if a granite rock is buried and subjected to high temperatures and pressures, it can turn into the metamorphic rock gneiss. When you stroll over the Frontenac Arch, you see lots of granite and its metamorphic product gneiss. You’ll also see marble, syenite, monzonite, migmatite, gabbro, quartzite and pegmatite2. As millions of years passed, the North American continent moved so that what is now Kingston was positioned near the equator. By the mid Cambrian Period (approximately 520 million years ago) this area became a shallow tropical sea –a stark contrast to its volcanic phase 700 million years before! By this time, life was in full bloom in

Fascinating Geological Features near Peterborough, Ontario

If you’ve ever wanted to time travel, looking at rock outcrops probably wasn’t your first thought. But if you know where to look, you can see a glimpse of history written in the rock layers.

Uncut natural diamond crystal embedded in a rock. On top of the photo text reads "Geoscience Today. Diamonds in the rough: what kimberlites tell us about Earth's interior"

Diamonds in the Rough: What Kimberlites Tell Us About Earth’s Interior

Everyone recognizes a diamond when they see one. Mounted on a ring or embedded in a necklace, these gemstones are prized for their use in jewelry around the world. What many people don’t realize, however, is that diamonds offer much more than commercial value. While the use of diamonds has been traced back to ancient times, large-scale modern diamond mining began in the late 1860s with the discovery of diamonds in Kimberly, South Africa. The rock from which the diamonds were extracted was creatively named kimberlite, after the town. Today, kimberlite is by far the most important source of naturally occurring diamonds, and deposits are found around the world. Diamonds originate from deep in the mantle, hundreds of kilometres beneath Earth’s surface. A common misconception is that diamonds are formed through the metamorphism of coal. This is not the case – although they are both composed of carbon, coal deposits are a result of the burial of plants, whereas diamonds are much older than the first plants on Earth! The journey of a diamond from the mantle to the surface is fascinating, and to properly set the stage, we need to first learn about plate tectonics. Large, rigid continental plates move slowly on Earth’s surface, repeatedly reshaping our continents over millions of years. In some parts of the continental lithosphere, there are massive and ancient blocks that haven’t been a part of subduction or continental rifting processes in billions of years. These are called cratons, and they form the geologically stable interiors of present-day continents. Cratons are found on all continents, including North America; for example, the Superior Province extends across Ontario and Manitoba and forms the core of the Canadian Shield. Typically, cratons are older than 2.5 billion years, meaning they come from a geological eon called the Archean. These cratons are thick enough to reach into the mantle, creating the perfect environment for diamonds to grow – anywhere else, and the pressures and temperatures are not suitable for the crystallization of carbon atoms in diamond form. It’s on the surface of these ancient cratons that diamond-rich kimberlites are found, but the kimberlites themselves are significantly younger than their Archean hosts; most are younger than 150 million years old. So how did they get there? Transporting a diamond from beneath an Archean craton to the surface of Earth is no easy feat, not least of all because the conditions of Earth’s surface are far below a diamond’s “comfort zone”, so to speak. If you were to bring a diamond to the surface at normal geological speeds, it would convert to graphite, the physical arrangement of carbon atoms that is stable at normal pressure and temperature conditions. To keep its diamond passengers happy, the magma must follow a few rules. Kimberlite magmas are full of volatiles, like water and carbon dioxide, and are more magnesium-rich than typical magmas. This type of chemistry produces low-density, low-viscosity magma that wants to separate from the mantle and rise to the surface in a truly remarkable way. Geological models show that kimberlitic magma begins to move upward at speeds ranging from 4–20 metres per second, propelled to even faster speeds by decreasing pressures towards an eventual 200 m/s explosive eruption on the surface. Assuming a starting depth of about 300 kilometres below the surface, a kimberlite could complete its diamond delivery within 15 hours! Considering that many geological features occur over millions of years, kimberlites move from the mantle to the surface relatively instantaneously. The combination of the unique volatile-rich magma chemistry and rapid ascent help to keep the diamonds stable, so they don’t convert to graphite or dissolve into the magma. This eruptive transport gives kimberlite pipes their characteristic “carrot” shape that is sometimes accompanied by a fallback of ejected pyroclastic material, like ash and rock fragments. Since diamonds do not crystallize within the original kimberlite magma and are instead picked up from the mantle as the magma ascends, they’re called xenocrysts, or foreign crystals. But while diamonds tend to get most of the attention, kimberlites can also carry other mantle rock fragments (xenoliths) to the surface. In fact, diamonds themselves often contain mineral inclusions, and while these are heartlessly referred to as flaws by a jeweller, they can be immensely important for understanding the pressure and temperature conditions of diamond growth. So, not only are kimberlites an important source of economic geology, but they can also provide geologists with information about the chemistry and conditions of the deep mantle that we would otherwise be unable to observe. Sadly, there hasn’t been much kimberlite activity in the last 50 million years, which means that the diamonds on our surface today are likely the only ones we’ll ever find on Earth. Even though kimberlite deposits occur on all continents, they can be somewhat difficult to track down. Rocks from the mantle tend to be unstable on the surface of Earth, so even though kimberlites are much younger than their surrounding rock, their composition makes them more vulnerable to weathering and erosion processes. However, specific minerals in kimberlites, like garnet and ilmenite, can survive weathering and in the case of many deposits in Canada, glacial transport. When the kimberlite deposit is hit by an advancing glacier, resistant minerals from the kimberlite are carried along by the ice and exploration geologists can follow the path of these minerals against the direction of glacier transport to find the source kimberlite pipe. Indicator minerals are abundant in kimberlites and relatively rare in other igneous rocks, making them a very useful tool for finding a kimberlite pipe that today might be a crater filled by water or vegetation. This method, also known as drift prospecting, is widely used across Ontario and the northern territories to search for diamond deposits because of Canada’s extensive glacial history. While diamonds are relatively rare and difficult to find on Earth, they’re actually exceedingly common in space. However, at a billionth of a meter in diameter, they’re nowhere near big enough for an

Rotating GIF of the Earth with the supercontinent Pangaea. Text over the Earth reads "Geoscience Today. How the Earth's last supercontinent broke apart to form the world we have today."

How the Earth’s last supercontinent broke apart to form the world we have today

Author: Alexander Lewis Peace, Assistant Professor (Structural Geology), McMaster UniversityThis article is republished from The Conversation under a Creative Commons license. Read the original article. Pangaea was the Earth’s latest supercontinent — a vast amalgamation of all the major landmasses. Before Pangaea began to disintegrate, what we know today as Nova Scotia was attached to what seems like an unlikely neighbour: Morocco. Newfoundland was attached to Ireland and Portugal. About 250 million years ago, Pangaea was still stitched together, yet to be ripped apart by the geological forces that shaped the continents as we know them today. For many years, geologists have pondered how all the pieces originally fit together, why they came apart the way they did and how they ended up spread across the globe. As an assistant professor in structural geology, I research plate tectonics — specifically how and why continents break up — and the related igneous rocks, natural resources and hazards. Puzzle Pieces We know that Nova Scotia and Morocco were once attached because their coastal areas — or margins — match up perfectly. We can also trace their path from the structure of the ocean floor now separating them. Today, we are much closer to understanding the shifting of the continents, including the movement of land masses, but there is still much to learn. The science of exactly why they ended up 5,000 km away from each other — and how other parts of the continental jigsaw puzzle pulled apart the way they did — has been extensively researched and debated. One camp believes the continents were dragged apart by the movement of tectonic plates driven by forces elsewhere. The other group believes that hot material from deeper underground forced its way up and pushed the continents apart. Whether one theory or the other or some combination of both is correct, this much is certain: whatever happened, didn’t happen quickly! Plate tectonics is an ongoing story that unfolds by mere millimetres each year. The change has added up over eons, placing us where we are today — still drifting, though almost imperceptibly. The North Atlantic An area of especially intensive study and lingering mystery is the North Atlantic — the area bounded by Greenland, Eastern Canada and Western Europe — where the final stages of Pangaea’s breakup played out. Curiously, perhaps, it is the region that spawned much of the geoscience that would successfully be applied to understanding the continental makeup of other regions of the world. When the North Atlantic began opening up, the continent started separating along the west side of Greenland. It then stopped and instead continued opening between eastern Greenland and Europe. Why? To solve this and related questions, two colleagues and I brought together about 30 researchers from many different fields of geoscience in the North Atlantic Working Group. Our research team includes geophysicists (who apply physics to understand processes in the Earth), geochemists (who apply chemistry to understand the composition of the materials that make up the Earth) and many others who study the structure and evolution of the Earth. To date, the North Atlantic Working Group has held a number of workshops and published a set of papers that propose a new model for answering some of the long-unanswered questions about what happened in the North Atlantic. Structural Inheritance Our North Atlantic Working Group was able to draw many types of data together and to tackle the problem from multiple angles. We concluded that most important geological events were strongly influenced by earlier activity — a process called “inheritance.” Throughout the history of the Earth, the continental landmasses have several times come together and then subsequently been torn apart. This process of amalgamation and subsequent dispersal is known as a “supercontinent cycle.” These previous events left behind scars and lines of weakness. When Pangaea was stressed again, it tore open along these older structures. While this process was suggested in the early days of plate tectonic theory, it is only now becoming clear just how important and far reaching it is. At the largest scale, the tear that formed the North Atlantic started first to the west of Greenland. There, it hit ancient mountain belts that would not break apart. There was less resistance to the east of Greenland, which opened like a zipper and eventually took up all the widening to form the North Atlantic Ocean. In addition, relics from these previous plate tectonic cycles left remnants deep in the Earth’s mantle that were susceptible to melting, explaining much of the widespread molten rocks that accompanied breakup. And at the smaller scale, it appears that the hydrocarbon bearing basins left behind on the continental margins were also influenced by previous events. Much of what we know about this was gathered in the search for oil and gas. Our most detailed knowledge comes from coastal areas closest to the markets where those commodities are processed and sold, and most of it has been obtained since the 1960s, using post-war technology to scan the bottom of the oceans. These economic factors mean that our knowledge of the subsurface drastically diminishes beyond Newfoundland. North of that, there is much to explore and to understand, where the answers to the remaining mystery of how we got here lie miles beneath the waves. I am a structural geologist leading the McMaster Structural Geology and Tectonics Group, in the School of Earth, Environment and Society at McMaster University. I research deformation processes and associated hazards as well as resources. I am particularly interested in rifting and breakup, rift-related magmatism, seismic hazards, and structural inheritance. Geographically, I have worked around the North Atlantic, with a particular emphasis on Eastern Canada. The nature of my work requires a multifaceted approach incorporating a wide variety of approaches and methodologies such as: seismic interpretation, field-based studies, numerical modelling, petrology, structural modelling and geochemistry.

Where are the dinosaurs?

Dinosaurs were some of the biggest animals to ever roam our planet. This massively large group of reptiles were around from the late Triassic Period (approximately 230 million years ago) until they went extinct at the end of the Cretaceous Period, approximately 65.5 million years ago (not including their flying descendants, which evolved into today’s birds!). For a remarkable 165 million years, they were seemingly ubiquitous; dinosaur fossils have been found on every continent! When dinosaurs first evolved, Earth’s plates were arranged into one large continent called Pangea. This single-continent arrangement no doubt facilitated their migration to all corners of the globe. It should stand to reason therefore that if I start digging in my backyard here in London, Ontario, I should eventually find some kind of dinosaur fossil, should it not? Turns out, the answer is a disappointing no. Only disappointing, though, if dinos are your only area of interest. Don’t get me wrong, I love dinosaurs (although I would not want to meet one in a back alley. Or even a front alley); however, there is still a treasure trove of fossils just waiting to be uncovered here in Ontario. The fossils here are just much, much older than any dinosaur, because the time they lived in and thus the rocks that their remains eventually became fossilized within are much older. The rocks in southwestern Ontario range in age from the late Ordovician Period (about 455 million years) to the Late Devonian Period (about 360 million years). That is roughly 205-130 million years before the first dinosaur strutted on the scene! If there are no dinosaur fossils to be found in southwestern Ontario, does this mean that dinosaurs never lived here at all? Fear not. Ask any paleontologist, and they will all agree that dinosaurs almost certainly did live in what is now Ontario, Canada. The Mesozoic Era, sometimes colloquially called the Age of the Dinosaurs, lasted approximately 165 million years. During such a long geological time span, there were no doubt times of deposition that added to the rock record. Given that there would have been many billions of individual dinosaurs during that time, the remains of many little and big critters would have absolutely been buried in the sediments and later undergone fossilization across Ontario. So, the big question remains: where are the dinosaurs? Up until about 2.5 million years ago, these fossilized dinosaur bones were likely still in the rocks in southern Ontario, just waiting to be discovered by future paleontologists. But then something big happened. Something really big. Things started to get very cold. Global temperatures began to drop significantly, and ice sheets started to grow on the continents. The cause of this change to colder conditions isn’t as clear as you’d think for something that occurred relatively recently (at least in geological terms that is). If you ask three different respected geologists why, you might get three slightly different respectable answers. That doesn’t mean that two of them are wrong, it just means that the cause is likely a result of an interplay of different factors that all contributed to lower global temperatures. The position of Earth’s continental plates no doubt played a big factor in the overall cooling of the planet, as their arrangement greatly affects oceanic and atmospheric circulation patterns. Other variables such as atmospheric CO2 levels and even predictable changes to Earth’s orbit could have facilitated the cooling process. In North America, the Laurentide ice sheet covered most of Canada and some parts of the United States a number of times, as it advanced and retreated repeatedly in cycles of growth and shrinkage in response to climatic conditions. You can imagine the havoc that a sheet of ice reaching a few kilometres in thickness would have on the ground as it makes its way forward and backward! The ice sheet literally scraped many layers of rock away, turning whatever got in its way into a fine powder called “rock flour”. All those poor dinosaur fossils that waited so patiently to get their place of honour in a paleontology museum were instead ground up into dust. Far be it from the scientific community to see this as a bad thing. Although glacial activity removed the fascinating rocks layers of the dinosaur-saturated Mesozoic Era here in Ontario, it ended up exposing the just-as-fascinating rock layers of the even older Paleozoic Era! The rocks that lie at or near the surface in southwestern Ontario range in age from the Upper (or late) Ordovician Period (about 455 million years old) around the Belleville to Peterborough area and get progressively younger as you drive southwest towards the Arkona area, where they are late Devonian in age (about 360 million years old). Although the fossils found in these rocks differ among species, there are many common types of fossils found in many of the limestone, dolostone, and shale outcrops throughout southwestern Ontario, from Ordovician to Devonian rock units. Some of the most common types of fossils found in southwestern Ontario are corals. Although they look like plants, corals are actually marine animals that usually lived attached to the seafloor. The fossilized corals here in southwestern Ontario are either tabulate (colonial-type) or rugose (solitary and colonial type) corals, and if you find them, it can tell you quite a bit about what the environment was like when they were alive. Since they thrive in relatively shallow, warm, marine seas, we can reconstruct their living conditions and make some accurate conclusions about the environment when these rock units were deposited. There are also many other fossils to be found in these rocks, such as brachiopods, gastropods, bivalves, crinoid parts, trilobites, bryozoans, and much more. The animation here shows what life could have looked like in the shallow, tropical seas of the Devonian Period, in southwestern Ontario. This is all fine and dandy, but the question still remains: where are the dinosaurs? To find them, you’ll need either a good-working car or a plane ticket; however, you

Geo Q&A: What are ice volcanoes?

If you’ve ever walked on the shoreline of one of the Great Lakes in the winter, you might have seen some inconspicuous mounds of ice on the water. These mounds, often forming in lines parallel to the shore, are known as ice volcanoes. Although they don’t spew fire like their rocky counterparts, if conditions are right, ice volcanoes can erupt icy cold water up to 10 metres high! They are typically conical in shape, like a stratovolcano, and have a hole going down the middle. What are the conditions for an ice volcano to form? Ice volcanoes can grow in a matter of hours—but only if the conditions are right. Usually, ice volcanoes only form on freshwater lakes because salt water has a lower freezing temperature. The lake must not be completely frozen, because they depend on wave action to form. It also must be cold enough outside for the spray from the waves to freeze into ice. If all these conditions are present, then there is the potential for an ice volcano to form. How do ice volcanoes form? Firstly, water freezes on the edge of the lake forming an ice shelf. The waves from the lake hit the ice shelf and go over and underneath it. When the water flows under the shelf, it sprays up through any cracks or holes in the ice. The spray from the water freezes on top of the shelf around any cracks or holes. If this process continues for long enough, the ice can grow into a mini volcano surrounding an existing hole! Where can I go to see them? If you want to see an ice volcano, be sure to keep a safe distance away and always stay on shore. The best place to see ice volcanoes is on the southern shores of Lake Erie and Lake Ontario. When the onshore wind is above 40km/hour and the temperature is below freezing, there are often rows of volcanoes by the shore. They can also form over sand bars or rocky reefs, although this is less common. This process is similar because the water is pushed upward under an ice shelf as it reaches shallower depths. From shore, you might even be able to locate a sand bar by the distinctive row of volcanoes on top of it. Why are ice volcanoes dangerous? Although icy cold spray from an erupting volcano may not be pleasant, the real danger from ice volcanoes is getting stuck inside one. If someone were to climb a volcano and fall inside the mouth, it would be extremely difficult for them to get out of the cold lake water surrounded by ice. Ice shelves are often unstable and cannot hold much weight. It is very important to never try to walk on an ice shelf or climb ice mounds. Always view them safely from shore. Why are ice volcanoes important? Ice volcanoes are useful in helping protect shorelines from erosion caused by waves and storms. While this protection doesn’t last long because the life of an ice volcano is relatively short, their presence still contributes to reducing shore erosion. Geoscientists study how erosion impacts the stability of shorelines and slopes in order to protect infrastructure from damage. If you’re curious about how geoscientists research and protect oceans, lakes, rivers and groundwater, checkout this video from GeoscienceINFO.com: Can we see ice volcanoes in other places? The Great Lakes are an excellent location to see ice volcanoes, but that’s not the only place you’ll find these types of structures. Astronomers have seen similar formations on other planets and celestial bodies! Off Earth, these formations are called cryovolcanoes, literally meaning “cold volcano.” They don’t only spew water, they can also erupt other volatiles like methane and ammonia. How do cryovolcanoes form? Similar to ice volcanoes on Earth, the temperature must be cool enough to freeze volatiles like water, methane, and ammonia. This most often happens on planets on the outer edges of solar systems, like the dwarf planet Pluto, or on moons and asteroids. The essential elements of cryovolcanoes are the same as ice volcanoes on Earth: an icy cone with liquid erupting up from underneath. But the actual formation of cryovolcanoes can be quite different. It has been theorized that a process called tidal friction is responsible for the formation of some cryovolcanoes. Jupiter’s moon Europa is made up of a worldwide ocean of liquid water or slushy ice with an overlying icy crust. The liquid under the crust moves due to the gravitational pull of Jupiter, creating tides. The moving liquid puts pressure on the ice, making cracks and fissures. As the liquid sloshes through these cracks in the crust and freezes, cryovolcanoes grow around the cracks and holes. However, tidal friction isn’t the only possible explanation for the formation of cryovolcanoes. If the inside of a planet is hot enough, materials that are melted will rise to the surface and create cryovolcanoes, similar to how magma rises through the mantle on Earth. There are two potential sources of heat on these celestial bodies. The first is caused by the decay of radioactive elements creating radiogenic heat. The second is heat left over from the formation of the planet, called primordial heat. Why are cryovolcanoes important? Cryovolcanoes can tell us a lot about the makeup of celestial bodies. For example, the finding of a giant cryovolcano on Saturn’s moon Titan helped to explain a prexisting mystery of the moon. The atmosphere of Titan has a large amount of methane in it, but since methane breaks down in sunlight, there should be less methane in the atmosphere than there is. The presence of the cryovolcano suggests that the methane is replenished from the interior of the planet by eruptions from the cryovolcano. Cryovolcanoes can help scientists to understand the mechanisms that create formations on celestial bodies. The beauty of ice volcanoes If you want to see ice volcanoes in action, go to the shore of a Great Lake this winter.