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Transcript
Earth Systems The Earth’s resources were determined when the planet formed. • Earth is ~4.6 Billion years old • Almost all of the elements currently found on the planet were present during formation. • As the forming Earth cooled, heavier elements condensed due to gravity and settled based on mass. • Ex. Iron sank towards the center and silica settled towards the surface. • Gaseous elements became the atmosphere The Earth’s Layers • This settling by mass resulted in distinct vertical layers • Core - the innermost zone of the planet made of nickel and iron. • Mantle - above the core containing magma • Crust - the outermost layer of the planet. The Earth’s Layers • Asthenospherethe outer part of the mantle, composed of semimolten rock. • Lithosphere- the brittle outermost layer of the planet Lithosphere • Made up of several large plates and numerous small plates • Includes the upper mantle and crust • Contains soil on the upper crust which is what allows life on the planet to exist because they contain the elements required for life Earth is dynamic and constantly changing • Earth’s geologic cycle consists of 3 major processes: 1. Tectonic Cycle 2. Rock Cycle 3. Soil formation Convection and Hot Spots • Despite being 4.6 byo, the planet remains very hot at its center • The heat causes hot magma plumes to well upward from the mantle producing hot spots • Hot Spots: places where molten material from the mantle reaches the lithosphere Theory of Plate Tectonics • States that the Earth’s lithosphere is divided into plates, most of which are constantly in motion • Tectonic Cycle – The sum of the processes that build up and break down the lithosphere Plate Tectonics • The lithosphere is broken into plates: • Oceanic Plates: Lie primarily beneath oceans • Crust is dense and rich in iron • Continental Plates: Lie beneath land masses • less dense and has more silicon dioxide Continental plates are lighter and will rise above oceanic plates Plate Tectonics • Convection: the movement of hotter and less dense material to rise, and colder, denser material to sink which results in the transfer of heat. • Where oceanic and continental plates come together, subduction occurs • Subduction: Plates passing under one another Consequences of Plate Movement • As a plate moves over a geologic hot spot, heat from the rising mantle plume melts the crust and forms a volcano • Volcano: a vent in the Earth’s surface that emits ash, gases, and molten lava. Plate movement over a hot spot • Hawaiian islands are an example of how land can form over hot spots due to volcanic eruption • Geologically, this is how all land originally formed • The eruption and cooling of molten lava Types of Plate Contact • Divergent plate boundaries- when plates move apart from one another. • Convergent plate boundaries- when plates move toward one another and collide. • Transform fault boundaries- then plates move sideways past each other. Divergent Boundaries • Occur between oceanic plates • Plates move away from each other, new magma rises and cools to form new lithosphere • This is called seafloor spreading Convergent Boundaries • If oceanic collide with continental, a coastal mountain range will form because the lighter continental plate will rise on top of the heavier oceanic plate which will subduct • If 2 continental plates collide, both margins will rise forming a mid-continental mountain range Transform Fault Boundaries • Transform boundaries are where plates slide against each other • Faults- a fracture in rock across which there is movement. • Earthquakes- occur when the rocks of the lithosphere rupture unexpectedly along a fault. The Rock Cycle • Rock cyclethe constant formation and destruction of rock. The Rock Cycle • Igneous rocks- rocks that form directly from magma. • Sedimentary rocks- form when sediment such as mud, sands, or gravels are compressed by overlying sediments. • Metamorphic rocks- form when sedimentary, igneous or other metamorphic rocks are subjected to high temperatures and pressures. Weathering and Erosion Weathering- when rocks are exposed to air, water, certain chemicals or biological agents that degrade the rock. Weathering and Erosion • Physical weathering- the mechanical breakdown of rocks and minerals. • Chemical weathering- the breakdown of rocks and minerals by chemical reactions. Erosion • Erosion- the physical removal of rock fragments from a landscape or ecosystem. Wind, water, ice transport and living organisms can erode materials. • Deposition- the accumulation or depositing of eroded material such as sediment, rock fragments or soil. Soil • Soil is important because it • Is a medium for plant growth • Serves as a filter for water • A habitat for living organisms • Serves as a filter for pollutants The Formation of Soil • Factors that determine the formation of soil: • Parent material- what the soil is made of influences soil formation • Climate- what type of climate influences soil formation • Topography- the surface and slope can influence soil formation • Organisms- plants and animals can have an effect on soil formation • Time- the amount of time a soil has spent developing can determine soil properties. The Formation of Soil • Parent Material- the rock material from which soil is derived. Soil Horizons • As soils form, they develop characteristics layers. Soil Horizons • O horizon- (organic layer) composed of the leaves, needles, twigs and animal bodies on the surface. • A horizon- (topsoil) the zone of organic material and minerals mixed together. • B horizon- (subsoil) composed primarily of mineral material with very little organic matter • C horizon- (parent material) the least weathered horizon and is similar to the parent material. Physical Properties of Soil • Texture- the percentage of sand, silt and clay the soil contains. Physical Properties of Soil • Porosity- how quickly the soil drains (which depends on its texture)