Earth Layers PDF

**Earth Layers** - The Earth is divided into four main layers. - Crust - Mantle - Outer core - Inner core **The Mantle** \*The mantle is the largest layer of the Earth. It is 2900km thick. \*It includes the lithosphere and athenosphere. \*It is relatively flexible-it flows like ve...

**Earth Layers** - The Earth is divided into four main layers. - Crust - Mantle - Outer core - Inner core **The Mantle** \*The mantle is the largest layer of the Earth. It is 2900km thick. \*It includes the lithosphere and athenosphere. \*It is relatively flexible-it flows like very viscous liquid. \*It is very hot-1600°F at the top and 4000°F towards the center of the Earth. **The Crust** \* The Earth\'s crust is the outermost surface. \*It is a very thin layer of solid rock. It is the thinnest layer of the Earth. \*The crust is 5-35km thick beneath the land and 1-8km thick beneath the oceans. \* The crust of the Earth is broken into many pieces called plates. The movement of these plates causes earthquakes. **The Core** \* The core of the Earth is like a ball of very hot metals. The core is divided into 2 layers-Outer and Inner. \* The core is SO hot and has SO much pressure that if you were to go there-you would be squished into something even smaller than a marble. **The Inner Core** \* The inner core is solid metal due to the extreme heat and pressure. \* It is composed of iron and nickel. It is responsible for the magnetic field the Earth generates. **The Outer Core** \* The outer core is liquid metal iron and nickel with 10% sulfur and/or oxygen. \* It is very hot- 4000-9000°F. \* The outer core is 2,250km thick. **The Asthenosphere** \* The athenosphere is the part of the mantle underneath the lithosphere. \* It is made of molten rock and metal so that it \"flows\" like hot asphalt. \* The athenosphere is the part of the mantle that moves and causes the tectonic plates of the crust to move as well. **The Lithosphere** **\*** The lithosphere is composed of part of the crust and the upper part of the mantle (the top 100 km). \* It is composed of hard, brittle rocks. **2 Types of Crust:** There are two types of crust: the thicker but less dense continental crust and the oceanic crust which is relatively thinner but denser than continental crust. - The lithospheric plates move at a very slow but continuous rates of a few centimeters a year. - The movement of the plates are driven by the unequal distribution of the heat within the Earth. **Continental Crust** \- thick, less dense than oceanic crust and mostly old -thick under the continents -Is mostly composed of **GRANITE** **Oceanic Crust** -thin, denser sinks under continental crust and young \- thick under the oceans \- is mostly composed of **BASALT** A diagram of a structure Description automatically generated with medium confidence **Plates Tectonics Theory:** Plate Tectonics Theory is the theory which states that the Earth\'s outer layer or the lithosphere consists of plates that move relative to each other and interact at various ways thereby producing earthquakes, volcanoes and mountain ranges. According to Plate Tectonics Theory: the uppermost mantle, along with the crust above it behaves as a strong, rigid layer known as the LITHOSPHERE; the lithosphere overlies a weaker region in the mantle known as the **ASTHENOSPHERE**; and the lithosphere is broken into numerous segments are called **TECTONIC PLATES**, which are in motion and continually changing in shape and size. The plates move at about 1 to 10 cm annually. - Major interactions of the plates happen along the **boundaries.** - Mountain ranges, volcanoes and earthquake epicenters are found along plate boundaries. 1\. **Geology** - The scientific study of the origin, history, structure, and composition of the earth. 2\. **Crust** - The solid uppermost layer of the earth. 3\. **Mantle** - The layer of the earth between the crust and the core and has a property called plasticity. 4\. **Core** - The innermost layer of the earth. 5**. Lithosphere** - The outermost rigid layer of the earth, consisting of the crust and the upper mantle. 6\. **Plates** - A section of the earth\'s lithosphere that is in constant motion along with other sections. 7\. **Tectonic** - Referring to the forces or conditions within the earth that cause movements of the plates. 8\. **Trench** - A long, steep-sided valley on the ocean floor. 9\. **Tsunami** - A Japanese term for \"big wave in the port,\" generated during undersea quakes. 10\. **Volcano** - A mountain or hill, typically conical, with a crater or vent through which lava, rock fragments, hot vapor, and gas erupt. 11\. **Mountain range** - A chain of mountains (2 words). 12\. **Earthquake** - A vibration of the earth due to the rapid release of energy. 13\. **Boundary** - Borderline. 14\. **Mid-ocean ridge** - A long mountain range on the ocean floor, extending almost continuously through the North and South Atlantic Oceans, the Indian Ocean, and the South Pacific Ocean. OCEANIC-CONTINENTAL CONVERGENCE -The bending of a denser leading plate towards the mantle is called **SUBDUCTION** process. -The leading edge of the oceanic plate bends toward the mantle since it\'s denser than the continental plate. -The continuous grinding of plates against each other will cause the occurrence of earthquakes. -One important feature formed at the oceanic crust is a **Trench**, also known as **submarine valleys**. -This allows the magma to rise and reach the edge of the continental plate forming **VOLCANIC ARC**. -Addition of volatile material such as water will cause the magma to become less dense. OCEANIC-OCEANIC CONVERGENCE -Involves the sinking of oceanic lithosphere beneath another plate of oceanic lithosphere. -Converging oceanic plates will cause formation of trenches, and these trenches will become sources of earthquakes. -The leading edge of the subducted plate will eventually reach the mantle causing it to melt and turn into **magma**. The molten material will rise to the surface creating a **Volcanic Island Arc** parallel to the trench. -Underwater earthquakes, especially the stronger ones, can generate **Tsunamis or Harbor Waves**. CONTINENTAL-CONTINENTAL CONVERGENCE -Unlike the other types of convergent boundaries, subduction ceases for this type of convergence. -**No trench, no volcano, and no island arc** are created in this type of convergent plate boundary. -Instead it leads to the formation of large group of tall mountains called **mountain range**. -Collision of continental plates is associated with shallow earthquake activities. **Plate movement** EVIDENCES OF CONTINENTAL DRIFT THEORY - Geological Fit - Fossil Correlation - Coal Deposit - Glacier A Theory which states that continents were once part of a single large landmass that broke apart and have moved to their present locations. [Alfred Lothar Wegener] -1880-1930 A German polar researcher, geophysicist, and meteorologist. Originator of the Continental Drift Theory **The evolution of the supercontinent Pangaea to the present-day distribution of continents.** PERMIAN 250 million years ago TRIASSIC 200 million years ago JURASSIC 145 million years ago CRETACEOUS 65 million years ago PRESENT DAY Pangaea is the name given to the single large landmass that was present 200 million years ago. Pangaea, a Greek word which means \"All Earth\" **EVIDENCES OF CONTINENTAL DRIFT THEORY** **Geological Fit** -Rock terrains of separate continents seem to match up. -Example include the Appalachian Mountains of east North America linked with the Scottish Highlands. -Is the matching of large- scale geological features in different continents. -Coastline of South America and West Africa seem to match up. **Fossil Correlation** \- Fossils are the preserved remains of plants and animals whose bodies were buried in sediments, such as sand and mud, under ancient seas, lakes and rivers. -[Alfred Lothar Wegener] mapped-out the distribution of four Permian and Triassic Fossil groups and used it as biogeographic evidence for continental drift and land bridging. - Lystrosaurus - Glossopteris - Cynognathus - Mesosaurus **Coal Deposit** -Coal is a black or brownish-black sedimentary rock that formed when dead plant matter decays and is converted into coal by the heat and pressure of deep burial over millions of years. -The existence of coal deposits in Antarctica suggested that it was once located near the region of the Earth where the climate is enough to support complex life forms such as plants and tall trees. **Glacier** -Glacial Striations (scratches in the rocks) can be found that match in Brazil and West Africa. -Glacial deposits are also very similar in India, South America and in the Vaal Valley in South Africa. **Convection Currents** Scientists believe that tectonic plates move because of convection currents that flow up from the core of the Earth and circulate under the asthenosphere. The tectonic plates can move slowly along the plate boundaries, pushing each other, sliding past each other, and drifting away from each other. The lithosphere at the divergent boundary will uplift and tear apart due to the rising of hot magma. The sinking of magma pulls down the tectonic plate at a convergent boundary. The movement of the lithospheric plate is attributed to mantle convection and is considered as one of the driving mechanisms for plate motion. **CONVECTION** also happens in the mantle. **MANTLE** is the second inner layer of Earth, made up of mostly hot rocks and magma. It is a very hot layer because of the heat generated by the core. The source of heat from the core is due to the decay or breakdown of radioactive elements. **EARTH\'S MECHANISM** deals with the forces acting on lithospheric plates to move in a particular direction. **WHAT MAKES LITHOSPHERIC PLATES MOVE?** **CONVECTION** is a heat transfer that involves the movement of fluid (liquid or gas) or molten rock from one place to another. happens due to the differences in the densities and the temperature of a specific gas or a fluid. due to this temperature difference, the hot fluid tends to rise as it expands, whereas the cold fluid tends to sink because it contracts. **OTHER FORCES THAT MOVE THE LITHOSPHERIC PLATES** **SLAB PULL** the presence of a heavier subducting plate pulls down the trailing slab into the subduction zone. **RIDGE PUSH OR GRAVITATIONAL SLIDING PROCESS**, the old oceanic crust becomes heavier than the new oceanic crust and sinks because of the weight of the raised ridge, which pushes down the older oceanic crust towards the trench at the subduction zone. **MANTLE** A layer beneath where the less dense hot molten material rises, and sinks. **ASTHENOSPHERE** A soft, weak, and plastic-like layer, the upper part of the mantle where lithospheric plates float and move. **MAGMA** Hot molten rocks formed beneath the Earth\'s surface. **LITHOSPHERE** A rigid layer of the Earth which comprises the crust and the uppermost part of the mantle. Convection is a kind of heat transfer caused by differences in temperature and density of a gas, fluid or molten rocks. Hot fluid materials rise because they are less dense while cold fluid materials sink because they are more dense. In the mantle, the repeating rising and sinking of materials creates a convection current driving the tectonic plates that ride on top to move slowly and constantly. **SEAFLOOR SPREADING THEORY** A theory which states that, a hot, less dense material from below the earth\'s crust rises towards the surface at the mi-ocean ridge. Magma flows out of the crack, cools down and becomes the new seafloor. This material flows sideways carrying the seafloor away from the ridge, and creates a crack in the crust. **The age, density, and thickness of ocean crust increases with distance from oceanic ridge.** **A geologist from Princeton University.** In the 1960s, Harry Hess along with Robert Dietz examined maps of the mid ocean ridge. He proposed that the ocean floors move like conveyor belts, carrying the continents with them. **Sonar**: A device developed in 1930\'s which determines the distance of an object under water by recording echoes of sound waves. **THE SONAR IS USED TO MAP THE OCEAN FLOOR** -Sonar bounces sound waves off underwater objects and then records the echoes of these sound waves -The time it takes for the echo to arrive indicates the distance to the object **What are the evidences that support this theory?** 1\. Rocks are younger at the mid-ocean ridge. 2\. Rocks far from the mid-ocean ridge are older. 3\. Sediments are thinner at the ridge 4\. Rocks at the ocean floor are younger than those at the continents. **MAGNETIC REVERSAL** Earth has a magnetic field. Over the history of the earth - its magnetic poles have reversed multiple times. Earth\'s magnetic field changes polarity (reverses) every 500,000 years or so. Geographic North becomes Magnetic South. These magnetic reversals are preserved in rock formed at mid-ocean ridges. Ocean floor has grown over time and moved away from mid- ocean ridge. **Core** is composed of iron, nickel, and sulfur. **Iron, and nickel** has magnetic property. Scientists began using **magnetometers** to measure the magnetism of the ocean floor in the 1950s. Scientists discovered that the magnetism of ocean floor around mid-ocean ridges was divided into matching stripes on either side of the ridge. A switch in the direction of Earth\'s magnetic field so that the magnetic north pole becomes the magnetic south pole. Also known as "magnetic flip\" **BASALT**, the once-molten rock that makes up most new oceanic crust, is a fairly magnetic substance. The specific magnetism of basalt rock is determined by the Earth\'s magnetic field when magma is cooling.