finals earth scie

• Exogenic Processes

  •These are external processes that occur at or near the surface of the Earth.

  •It includes degradation processes (weathering, mass wasting and erosion) and aggradation processes (deposition). These are external processes that occur at or near the surface of the Earth.
• 1. Weathering

  • It is the physical breakdown and/or chemical alteration of rocks at or near the surface of the Earth.

  • The disintegration and decomposition process act together, but one maybe dominant, depending on the climate.
• Physical Weathering

  • This happens whenever rocks are broken up without any change in their chemical composition.

  • Sometimes called mechanical weathering.

  • This type of weathering takes place in different ways depending on the factor that acts on the rock which includes pressure, warm temperature, water and ice.
• Block disintegration

  • a physical weathering that It is caused by successive heating and cooling that causes the expansion and contraction of rocks.
• Exfoliation

  • an example of physical weathering which is the stripping of the outer layer of rocks due to intense heating.
• Frost action / frost wedding

  Physical weathering this refers to the alternate freezing and thawing of water inside the joints of the rocks causing them to split into fragments or small particles.
• Chemical Weathering

  • It is the weakening or disintegration of rocks and the formation of new compounds or new substances caused by chemical reactions.
• Examples of Chemical Weathering

  • OXIDATION - Oxygen reacts with rock and changes its mineral composition.

  • CARBONATION - Formation of various types of carbonates, some of these carbonates are soluble in water
• Examples of Chemical Weathering

  • SOLUTION - some minerals in the rocks are directly dissolved in water.
• Biotic/Biological Weathering - the weathering of rocks caused by living organisms
• • HYDRATION - a chemical weathering that is the result of the absorption/combination and a particular substance on the rock, leading to change in shape.
• Exogenic Processes

  2. Mass Wasting

  •Refers to the downslope movement of rock, regolith, and soil because of gravity.

  • It is a natural process that occurs after weathering
• Classification of Mass Wasting

  • Fall - the free-fall movement of detached individual pieces of rock.

  • Slide - occurs when rock materials remain fairly coherent and move along well-defined surface.

  • Flow - happens when rock materials are saturated with water and move downslope as a viscous fluid.
• Exogenic Processes

  3. Soil Erosion

  • It refers to the removal of soil at a greater rate than its replacement by natural agencies.
• Types of Soil Erosion

  Wind erosion

  • Happens when winds carry large amount of fine soil particles away from a region, spreading it over adjoining cultivated land and destroying their fertility.

  Sheet erosion

  • It is the removal of thin layers of soil because of surface runoff and rain.
• Types of Soil Erosion

  Rill erosion

  • It is the removal of soil by action of concentrated running water. This process creates several centimeter-deep tiny channels called rills, which carry water during storms.

  Gully erosion

  • It is the removal of soil in water channels or drainage lines. The gullies gradually multiply and spread over a wide area. The land being dissected is called badlands or ravines
• Heat is seen as an energy from the motion of the molecules of bodies, such as Earth, that maybe transferred by conduction, convection and radiation. Such heat drives the internal processes of the planet.
• Three main sources of heat on Earth

  •Heat from the accretion of Earth during its formation

  • Frictional heating, caused by the sinking of core materials to the center of the planet

  • Heat from the decay of radioactive elements
• The temperature of Earth's layers increases with depth, reaching up to 7000°F at the core
• Volcanism

  • Is the eruption of molten rock (magma) onto Earth's surface through a vent.

  • The driving force of volcanism is the plate tectonic motion created by the movement of molten rocks in the mantle caused by thermal convection currents.
• • A volcano is a vent in the surface of the Earth where magma is expelled during a Volcanic eruption.

  • Lava is the primary material extruded from a Volcano in addition to Volcanic rocks, ash, and dust during volcanic eruptions.
• Deformation

  •refers to any change in the shape or size of a rock as a response to the stress.

  • The deformation may occur by either folding or faulting
• Folding in rocks occur when they are subjected to tectonic forces from opposite sides.

  Compressional stress causes squeezing

  Tensional stress causing stretching

  Shearing stress causes side-to-side side-to- movement.
• • Faulting is the result of the fracture or displacement of rob layer or strata along a fault line.

  Dip-slip faults - show vertical movement of the hanging wall and footwall. Examples are normal fault and reverse fault.

  Strike-slip fault shows horizontal and parallel displacements of the fault planes. An example of this is transform fault.
• Continental Drift Theory

  • It is the gradual movement of continents over time.

  • The upper layer of the crust is broken down into large slabs called plates, which sit on a fluid level of molten rock.

  • The movement of this lower molten layer, called plate tectonics, causes the plates to shift
• Alfred Wegener theorized that the continents once existed as a single landmass, which he called Pangaea
• Plate Boundaries

  Divergent boundary occurs when two tectonic plates move away from each other.

  Convergent boundary happens when two plate boundaries move or collide towards each other.

  • Transform Boundary occurs when two plates slide past each other
• Seafloor Spreading

  This is a geologic process in which tectonic plates split apart from each other as a result of mantle convection - the slow, churning motion of Earth's mantle.

  • Convection currents carry heat from the lower mantle and core to the lithosphere.

  • Sea floor spreading occurs at divergent plate boundaries
• Mid- Ocean Ridge

  • Large mountain ranges rising from the ocean floor as a result of seafloor spreading.

  • The Magnetism of mid- ocean ridges helped scientist identify the process of seafloor spreading in the early twentieth century