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Erosion, & Types of Weathering Chapter 10 Erosion A process where water, wind, or gravity transports soil (sediment) from its source The process by which rocks are broken down into smaller pieces There are 2 main types, chemical & Physical Weathering Mechanical Weathering The break down of rock into smaller pieces due to physical means – Frost wedging (water freezing in rock cracks) – Abrasion (other rocks or sediment rubbing against rock.) Chemical Weathering Rocks break as a result of a chemical change – Acid rain – Chemical decomposition – Gases in the air (oxidation) Deposition Is the process where material lays to rest Sediment is deposited in bodies of water and on land Chapter 6 The Rock Record Sedimentary Rock Layers This is a normal record of rock. Layers are undisturbed. The Geologic Column is a model of what rock layers should look like. Uniformitarianism A principle or rule that states that events that happened in the past can be explained by current earth (geologic) processes Earth Processes like erosion, weathering, and deposition remain uniformed and do not change. Catastrophism A principle that states that geologic changes happen suddenly. (natural disasters) They believed the Earth was only a few thousand years old. Catastrophic events formed the Earth, created volcanoes, mountains, oceans, etc. Relative Dating Determines which comes first. Determining if rock layers are older or younger Compare them to undisturbed rock around the world Principle of Superposition A principle or rule that states that younger rocks lie above older rocks in un-disturbed sequences As you move from top of rock layers to the bottom the rock layers get older SUPERPOSITION Uplift movement within the Earth that moves rocks to the surface Unconformities Is a disturbance in the layer of a rock. Represents thousands, to millions of years in missing time in the layers of a rock Can be created through: – Erosion and weathering (p159, figure 4) – Faulting- (earthquakes) – Folding (anticlines, synclines, and monoclines) – Tilting – intrusion Rock Intrusion A layer of molten rock (hardened magma) from the Earth’s interior that squeezes into existing rock and then cools. Melts surrounding layers Interrupts the rock time scale. Types of Unconformities Disconformity – part of a parallel rock layer is missing. (Layers may be eroded away and deposited elsewhere) Nonconformity- horizontal sedimentary rock layers lay on the eroded surface of intrusive igneous rocks or metamorphic rocks Angular unconformity- rocks are tilted or folded due to earthquakes or uplift (p 160) Terms Erosion Weathering Uplift Deforestation Mechanical weathering Chemical weathering Relative dating Uniformitarianism Superposition Intrusion Catastrophism Un-conformity Strip Mining Frost Wedging Abrasion