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A Brief Overview of Major Topics in Geology Definition Geology is the study of the Earth, the materials of which it is made, the structure of those materials, and the processes acting upon them. What Geologist Do? Geologists study earth processes: Many processes such as landslides, earthquakes, floods and volcanic eruptions can be hazardous to people. Geologists work to understand these processes well enough to avoid building important structures where they might be damaged. Geologists study earth materials: People use earth materials every day. They use oil that is produced from wells, metals that are produced from mines, and water that has is drawn from streams or from underground. Geologists conduct studies that locate rocks that contain important metals, plan the mines that produce them and the methods used to remove the metals from the rocks. Geologists study earth history: Today we are concerned about climate change. Many geologists are working to learn about the past climates of earth and how they have changed across time. This information is valuable to understand how our current climate is changing and what the results might be. Why Should We Care About Geology? What is your car made of? What are your houses made of? Where do you find diamonds and other precious stones? All of these things are possible because of Geologist who discovered them. “The Farther back you can look, the farther forward you are likely to see.” -W. Churchill What does this question mean to you? Our Earth Our Earth was formed about 4.56 billion years ago!!! The earth is divided into four main layers: Crust Mantle Outer Core Inner Core Earth’s Layers: Crust Crust: the outermost solid shell of a planet. We live on the very top of the crust. The crust is the thinnest layer of the Earth. It floats upon the softer, denser mantle. The Crust is about 30 miles deep. Crust Crust: Two Types of Crust Continental Crust: which forms the continents, and the areas of shallow seabed close to their shores, or all the land of the Earth. We live on the Continental Crust Oceanic Crust: is the land beneath all of the oceans of the Earth. It is much thinner, softer, and is denser than continental crust. Oceanic Crust Continental Crust Mantle The Mantle is below the Crust. It is about 1,800 miles(2,900 km) thick and makes up nearly 80% of the Earth's total volume. Mantle Mantle Upper Mantle: is about 665 miles thick and is made up of molten material which is a mixture of liquid-like rock. Since it is liquid-like, it is less dense than solid rock. Lower Mantle: is about 1357 miles thick and is made up of solid rock material. Outer Core Traveling still deeper within the Earth, we next would encounter the Earth’s outer core, which extends to a depth of around 3000 miles beneath the surface. It is believed that this outer core is made up of super-heated liquid molten lava. This lava is believed to be mostly iron, and nickel. Outer Core Inner Core Finally, we would reach the Earth’s inner core. The inner core extends 3,960 miles from Earths surface. It is believed that this inner core is a solid ball of mostly iron, and nickel. The Temperature is about 9032 - 10832 ºF (5000-6000 ºC)!!!! Inner Core Plate Tectonics Continental Drift The idea that continents move freely over Earth’s surface, changing their positions relative to one another. Continents can be made to fit together like pieces of a picture puzzle like the Atlantic coastlines of Africa and South America millions of years ago. The idea that continents were once joined together and have split and moved apart from one another has been around for more than 130 years. Pangea Plate Tectonics Definition: The theory that the earth's surface consists of plates, or large crustal slabs, whose constant motion explains continental drift, mountain building, volcanoes, etc. Earth’s Crust is broken up into plates that move the continents around slowly over time. Plate Tectonics: Lithosphere Lithosphere: The outer part of the Earth, consisting of the crust and upper mantle. Lithosphere Plate Tectonics: Asthenosphere Asthenosphere: A zone of the earth's mantle that lies beneath the lithosphere and consists of several hundred kilometers of deformable rock. The Asthenosphere is a thick layer of hot rock that is semi fluid- like. Lithosphere Asthenosphere Lithosphere Asthenosphere Plate Tectonics The Earth’s crust is divided up into “pieces” called Tectonic Plates which is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere (crust). The lithosphere is solid rock that sits on or “floats” on top of the semi fluid-like asthenosphere. Plate Tectonics shows how these “pieces” of lithosphere, or crust, move slowly over time and interact with each other. Plate Tectonics: Convection Convection: The cycle of movement in the asthenosphere that causes the plates of the lithosphere to move. Heated material in the asthenosphere becomes less dense and rises toward the solid lithosphere, through which it cannot rise further. It therefore begins to move horizontally, dragging the lithosphere along with it and pushing forward the cooler, denser material in its path. It is as if the lithosphere is a “floating” floor. The cooler material eventually sinks down lower into the mantle, becoming heated there and rising up again, continuing the cycle. Convection Think of convection like boiling a pot of water…. As water heats to its boiling point, the water rises to the top and then sinks to the bottom and continues this cycle. Plate Tectonics: Ridges and Plate Boundaries Mid-Ocean Ridges: a connected system of undersea volcanoes that roam over the Earth like the raised string on a baseball. It is a continuous 40,000-mile seam that encircles Earth and bisects the oceans. A mid-ocean ridge represents an area where, in accordance with plate tectonic theory, tectonic plates (lithosphere plates) move apart and new crust is created by magma (molten rock) pushing up from the mantle. Mid-Ocean Ridge Mid-Ocean Ridge Ridges and Sea Floor Spreading As magma from the asthenosphere rises at mid-ocean ridges, it creates new crust (or oceanic crust) and causes the sea floor to spread outward from the ridge. This is called Sea Floor Spreading. A mid ocean ridge is an example of Divergent plate boundary: locations where plates are moving away from one another. What Happens to Old Oceanic Crust? (Convergent Plate Boundary) As mid-ocean ridges slowly creates new lithosphere (crust), it pushes the existing crust outward towards the continents. Since oceanic crust is softer and more dense than continental crust, it submerges underneath continental crust. This process is called a Convergent Plate Boundary. Convergent plate boundary Plate Tectonics: Transform Plate Boundary Transform Plate Boundary: locations where two plates slide past one another. Plate Boundary Review Divergent Plate Boundary Convergent Plate Boundary Transform Plate Boundary http://www.youtube.com/watch?v=Lxq6Vdl0sr4 A video to help understand plate boundaries and how they move over millions of years. Geologic Time The Earth is about 4.6 billion years old!!! Geologic Time is divided up into Eons, Eras, and Periods. Eras Eras: an organized scale that divides the earth's history into 4 parts Precambrian (4.5 billion years ago- 542 million years ago) Paleozoic (543 to 248 mya) Mesozoic (248 to 65 mya) Cenozoic (65 mya to today) Precambrian Time Contains 3 Eras within this time period. 1. Hadean Era- (4.5 bya to 3.8 bya) During this time, Earth was just forming in the Solar system and was made out of gas and dust. 2. Archaean Era- (3.8 bya to 2.5 bya) Earth began to cool and formed rocks. The atmosphere was very different than it is today. The air contained many toxic gases that would be very harmful to humans. The first forms of life appeared during this time which were in the forms of bacteria. 3. Proterozoic Era- (2.5 bya to 543 mya) During this time, continents began to form, oxygen began to form in the atmosphere, and the first fossils appeared which were bacteria life forms. Precambrian Time Precambrian Paleozoic Era Contains 6 Periods within this time. 1. Cambrian (543 to 490 mya) Ordovician (490 to 443 mya) Silurian (443 to 417 mya) Devonian (417 to 354 mya) Carboniferous (Mississippian and Pennsylvanian) (354 to 290 mya) Permian (290 to 248 mya) 2. 3. 4. 5. 6. Paleozoic Era Mesozoic Era Contains 3 Periods within this time. 1. Triassic (248 to 206 mya) Jurassic (206 to 144 mya) Cretaceous (144 to 65 mya) 2. 3. During this Era, Dinosaurs were perhaps the most popular organisms. The began in the Triassic period but were not very diverse until the Jurassic period. Accept for birds, Dinosaurs became extinct during the Cretaceous period. Also during this time, the first flowering plants began. Mesozoic Era Cenozoic Era Contains 2 Periods 1. Tertiary (65 to 1.8 mya) Quaternary (1.8 mya to today) 2. The Cenozoic era is the most recent in geologic time. We are currently still in the Cenozoic ear (or the Quaternary period). The Cenozoic spans only about 65 million years ago, from the end of the Cretaceous and the extinction of dinosaurs to now. The era is also known as the Age of Mammals because the largest land animals have been mammals during this time. Cenozoic Era Types of Rocks Igneous Metamorphic Sedimentary Igneous Rocks Igneous Rocks Igneous Rocks form by crystallization of molten (melted) material; either magma (within the earth) or lava (on the surface of the earth). Igneous rocks are also formed when volcanoes erupt, causing the magma to rise above the earth's surface. When magma appears above the earth, it is called lava. Igneous rocks are formed as the lava cools above ground. Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets. As these pockets of magma cool slowly underground, the magma becomes igneous rocks. Types of Igneous Rocks Basalt is a fine-grained, dark- colored extrusive igneous rock composed mainly of plagioclase and pyroxene. Diorite is a coarse-grained, intrusive igneous rock that contains a mixture of feldspar, pyroxene, hornblende and sometimes quartz. Granite is a coarse-grained, light colored, intrusive igneous rock that contains mainly quartz and feldspar minerals Types of Igneous Rock Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form. Rhyolite is a light-colored, finegrained, extrusive igneous rock that typically contains quartz and feldspar minerals. Welded Tuff is a rock that is composed of materials that were ejected from a volcano, fell to Earth, and then lithified into a rock. It is usually composed mainly of volcanic ash and sometimes contains larger size particles such as cinders. Metamorphic Rock Metamorphic Rock Metamorphic Rocks are already existing rocks that have been altered or molded by lots of pressure, very hot temperatures, or chemical changes. Comes from the word “metamorphism”, which means "change in form". Types of Metamorphic Rocks Amphibolite is a non-foliated metamorphic rock that forms through recrystallization under conditions of high viscosity and directed pressure. Gneiss is foliated metamorphic rock that has a banded appearance and is made up of granular mineral grains. It typically contains abundant quartz or feldspar minerals. Marble is a non-foliated metamorphic rock that is produced from the metamorphism of limestone. It is composed primarily of calcium carbonate. Types of Metamorphic Rocks Quartzite is a non-foliated metamorphic rock that is produced by the metamorphism of sandstone. It is composed primarily of quartz. Schist is metamorphic rock with well developed foliation. It often contains significant amounts of mica which allow the rock to split into thin pieces. It is a rock of intermediate metamorphic grade between phyllite and gneiss. Slate is a foliated metamorphic rock that is formed through the metamorphism of shale. It is a low grade metamorphic rock that splits into thin pieces. Sedimentary Rocks Sedimentary Rocks Rock that has formed through the deposition and solidification of earth sediment, especially sediment transported by water (rivers, lakes, and oceans), ice (glaciers), and wind. Sedimentary rocks are often deposited in layers, and frequently contain fossils. Sedimentary Rocks form from the remains of other rocks, earth sand, and other earth materials. They are me most common rock type. They form over a long period of time and with a lot of pressure. Types of Sedimentary Rocks Conglomerate is made up of rounded pebbles cemented together. Sandstone is sand grains cemented together into solid stone. Limestone is made primarily of calcium carbonate or calcite. The most common source of this calcite is the shells of marine organisms. The most common sedimentary rock in the Bahamas!! The Rock Cycle