Copy-of-W4-Endogenic-Processes.pptx

Endogenic Processes  1. Describe the physical and chemical changes in rocks due to changes in pressure and temperature (metamorphism) and 2. Compare and contrast the formation of the different types of igneous rocks.  Write True if the statement is correct and False if it is incor...

Endogenic Processes  1. Describe the physical and chemical changes in rocks due to changes in pressure and temperature (metamorphism) and 2. Compare and contrast the formation of the different types of igneous rocks.  Write True if the statement is correct and False if it is incorrect. Use another sheet of paper for your answer. ____1. Burial metamorphism occurs when sediments are buried deeply enough that the heat and pressure cause minerals to begin to recrystallize and new minerals to grow but does not leave the rock with a foliated appearance. ____2. Regional metamorphism refers to large- scale metamorphism, such as what happens to continental crust along convergent tectonic margins. ____3. Contact metamorphism happens when a body of magma intrudes into the upper part of the crust. ____4. Dynamic metamorphism is the result of very high shear stress, as it occurs along fault zones. ____5. Metamorphism is the change of minerals or geologic texture in pre-existing rocks without the protolith melting into liquid magma. ____6. Plutonic igneous rock is formed from lithification. ____7. Scoria is a light-colored and coarse-grained rock. ____8. Igneous extrusive is also known as plutonic igneous rock. ____9. Magma that reaches the earth’s surface during a volcanic eruption is called lava. ____10. The collision of rock layers causes rocks to be folded, broken, and stacked on each other. METAMORPHISM Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form”. The original rock, protolith, is subjected to heat (temperatures greater than 150 to 200 °C) and a pressure of 100 megapascals (1,000 bar) or more, causing profound physical or chemical change. The protolith may be a sedimentary, igneous, or existing Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. They are classified by texture and by chemical and mineral assemblage (metamorphic facies). They may be formed simply by being deep beneath the Earth's surface, subjected to high temperatures and the great pressure of the rock layers above it. They can form from tectonic processes such as continental collisions, which cause They are also formed when rock is heated by the intrusion of hot molten rock called magma from the Earth's interior. The study of metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides information about the temperatures and pressures that occur at great depths within the Earth's crust. Some examples of metamorphic rocks are gneiss, slate, marble, schist, and  Metamorphism is the change of minerals or geologic texture in pre-existing rocks, without the protolith melting into liquid magma. The change occurs primarily due to heat, pressure, and the introduction of chemically active fluids. This occurs because some minerals are stable only under certain conditions of pressure and temperature. When pressure and temperature change, chemical reactions occur to cause the minerals in the rock to change to an assemblage that is stable at the new pressure and temperature conditions.  Burial metamorphism occurs when sediments are buried deeply enough that the heat and pressure cause minerals to begin to recrystallize and new minerals to grow but does not leave the rock with a foliated appearance. As metamorphic processes go, burial metamorphism takes place at relatively low temperatures (up to ~300 °C) and pressures (100s of m depth). Fig 1. Rocks that undergo burial metamorphism  Regional metamorphism refers to large-scale metamorphism, such as what happens to continental crust along convergent tectonic margins (where plates collide). The collisions result in the formation of long mountain ranges, like those along the western coast of North America. The force of the collision causes rocks to be folded, broken, and stacked on each other, so not only is there the squeezing force from the collision, but from the weight of stacked rocks. The deeper rocks are within the stack, the higher the pressures and temperatures, and the higher the grade of metamorphism that occurs. Rocks that form from regional metamorphism are likely to be foliated because of the strong directional pressure of converging plates.  Fig 2. Position of the lithosphere as it undergoes regional metamorphism S ource: openpress.usask.ca Subduction Metamorphism At subduction zones, where ocean lithosphere is forced down into the hot mantle, there is a unique combination of relatively low temperatures and very high pressures. The high pressures are to be expected, given the force of collision between tectonic plates, and the increasing lithostatic pressure as the subducting slab is forced deeper and deeper into the mantle. Fig.3. Movements of the Ocean lithosphere during subduction metamorphism Source: opentextbc.ca/ openpress.usask.ca Contact metamorphism happens when a body of magma intrudes into the upper part of the crust. Heat is important in contact metamorphism, but pressure is not a key factor, so contact metamorphism produces non-foliated metamorphic rocks such as hornfels, marble, and quartzite. Fig.4. Contact Metamorphism Source: openpress.usask.ca  Dynamic metamorphism is the result of very high shear stress, such as occurs along fault zones. Dynamic metamorphism occurs at relatively low temperatures compared to other types of metamorphism and consists predominantly of the physical changes that happen to a rock experiencing shear stress. It affects a narrow region near the fault, and rocks nearby may appear unaffected. Fig.5. Dynamic Metamorphism Source: quora.com IGNEOUS ROCK Igneous Rock got its name from a Latin word “ignis” which means fire. The parent material of ignoeus rocks is usually magma, a molten material from deep within the Earth that cools and hardens.There are many varieties of igneous rocks and they are given names based upon two things: texture (how big the crsytals are) and composition (what they made of)  a. Texture refers to the general appearance of an igneous rock. The texture of an igneous rock is strongly affected by the rate of cooling of the magma that results in the formation of crystals. b. Composition refers to the elements in the magma that directly affect the kind of mineral that is formed when the magma cools. Types of Igneous Rocks Igneous Rocks may be classified into two groups according to where the magma cools and solidifies.  A.Igneous Intrusive or Plutonic Igneous 1. Granite is one of the most important rocks in the crust. It is also the most common rock type. It is a light-colored and coarse grained rock. 2. Gabbro is dark-colored igneous rock often times called “ black granite”. The dark color is due to a higher content of iron and the magnesium but with a lower content of quartz.  1. Basalt as a specific rock is usually dark- colored, hard, fine-grained and with high specific gravity. This is due to the high content of iron and magnesium and some feldspar. 2. Obsidian that is formed from lava is also dark-colored but glassy, meaning it has no crystal. During early times, these rocks were used for weapons and tools was by shaping them into pointed and sharp-edged objects.  3. Pumice is characterized by the prescence of many air holes. This is because gas bubbles are trapped in the rock during the cooling process leaving tiny bubbles. 4. Scoria is formed in the same manner as pumice, but it has larger holes and is much denser and darker. Some magma rise and flow into the cracks in the crust but do not reach the surface; instead they harden deep inside the crust. They are called igneous intrusive or plutonic igneous. This rock cools slowly and take thousands or even million of years to solidify. Most common examples of igneous intrusive rocks. B. Igneous Extrusive also known as Volcanic Igneous Sometimes magma may reach the surface or erupt onto the surface from volcanoes. This extrusion onto the surface is called lava. When lava cools, it solidifies. Since solidification occurs at the surface of the Earth, the rock is called igneous extrusive or volcanic igneous. Most common examples of igneous extrusive.  Directions: Answer the following questions on a separate sheet. 1. What is metamorphism? __________ 2.How will the amount and type of metamorphism vary as you move across each environment? _______________ 3.How do the types of igneous rocks differ from one another? __________________