SCI EXAM REVIEW

• Geosphere


  Refers to the solid part of the Earth, including the rocks, minerals, landforms, and the processes that shape them
• Layers of Earth


  • Crust
  • Mantle
  • Core (inner & outer)
• Crust


  • Outermost layer of Earth where life exists
  • Thinnest layer - ranging from about 5-70 km in thickness
• Types of crust


  • Continental Crust
  • Oceanic Crust
• Continental Crust


  • Crust that makes up the continents and is about 40-70 km thick
  • Made up of light granitic rocks made up of mostly aluminum silicates
• Oceanic Crust


  • Crust that underlies the ocean floor
  • Average thickness of 5 km
  • Composed of dense basaltic rocks made up of magnesium silicates
• Mantle


  • Below the crust
  • A semisolid, rocky, and very hot layer
  • Thickest layer - measuring about 2900 or 80% of Earth and carries most of its mass
  • Composed of ferro-magnesium silicate rocks
• Mantle layers


  • Upper Mantle
  • Lower Mantle
• Upper Mantle


  • Relatively rigid and contains the asthenosphere
  • Allows the movement of tectonic plates
  • Mantle's top layer has a temperature of about 900 C
• Lower Mantle


  • Contributes to the overall convection and heat transfer within the Earth's interior
  • Going deeper into the mantle, the temperature increases from 1000 C - 3700 C
• Outer Core


  • Only liquid layer
  • Mostly made up of molten nickel and iron
  • About 2270 km thick
  • Temperatures ranging 3700 C - 4300 C
  • Responsible for the magnetic field
• Inner Core


  • Diameter about 1220 km
  • Composed mostly of solid iron and nickel
  • Extremely hot - 6000 C
• Lithosphere


  • Comprises of the crust and the uppermost part of the mantle
  • A rigid layer that can break under stress
  • Composed of tectonic plates
• Tectonic Plates


  • Composed of major and minor blocks that interact and create the tectonic activities on Earth
  • Many independent massive slabs of solid rocks that float on the semi-fluid mantle below them at a rate of 1-10 cm per year
• Asthenosphere


  • Below the lithosphere
  • About 180 km thick
  • Semi-fluid layer
  • Contains hot, molten rocks or magma
  • Can deform and reshape driven by heat energy, which circulates as convection currents, traveling upward from the hot lower mantle to the cooler upper mantle
  • This heat transfer mechanism helps drive the movement of tectonic plates, which is manifested as earthquakes
• Boundaries Between Layers of Earth


  • Conrad Discontinuity (Upper & Lower Crust)
  • Mohorovic / Moho Discontinuity (Lower crust & upper mantle)
  • Repetti Discontinuity (Upper & Lower mantle)
  • Gutenberg Discontinuity (Lower mantle & outer core)
  • Lehmann Discontinuity (Outer & Inner Core)
• Seismic Waves


  • Created by earthquakes, volcanic eruptions, and other tectonic processes
  • Knowledge on how they behave allowed scientists to learn about the Earth's layers
  • Detected by sensitive instruments called seismometers and recorded by seismographs
• Types of Seismic Waves


  • Body Waves
  • Surface Waves
• Body Waves


  • Primary Waves / P waves
  • Secondary Waves / S waves
• Primary Waves / P waves


  • First to be felt on earth; faster
  • Compressional / Longitudinal waves
  • Shake the ground back and forth in the same direction the wave is moving
  • Pass through solid and liquid sections
  • Refract or bend as they pass through liquids
• Secondary Waves / S waves


  • Transverse waves
  • Up-and-down motion perpendicular to the direction of the wave
  • Do not travel through liquids
  • Travel slower than P waves
• Surface Waves


  • Only travel on the surface
  • Used for geological studies such as earthquake damages and strength
  • They do not provide information about the Earth's interior
• Contraction Theory


  • One of the earliest theories on the changing geography and surface topography of Earth
  • Suggested that as Earth cooled after its formation, its surface contracted and wrinkled, these wrinkles being the mountain ranges on Earth
  • All features on Earth were formed during a single cooling event
• Continental Drift Theory


  • Proposed by Alfred Wegener in 1912
  • Asserted Pangaea
  • Based upon his observations: apparent fit of the coastlines of South America and Africa, similarities of plant and animal fossils in South America and Africa, similarities in the sequences of rock layers of opposite sides of the Atlantic Sea
  • Rejected because Wegener failed to provide evidence for the mechanism that drives the movement of plates
• Pangaea


  • Earth began as a single landmass or supercontinent
  • Surrounded by a vast sea or superocean called Panthalassa
  • Broke down into 2 smaller supercontinents, Gondwana and Laurasia
• Seafloor Spreading Theory


  • Proposed by Harry Hess in the 1960s
  • States that the seafloors or ocean floors, not the continents, move and carry the continents along
  • The ocean floor is continually moving and constantly regenerated from a spreading center
• Plate Tectonics Theory


  • Incorporates the continental drift and seafloor spreading theory
  • A scientific theory that explains how landforms are created from the movement of the Earth
  • The heat driving the convection currents is the radioactive decay underneath Earth
  • The earth's crust is broken into 7 larger plates and into several smaller plates
• Primary Plates


  • Eurasian Plate
  • Australian Plate
  • Pacific Plate
  • North American Plate
  • South American Plate
  • African Plate
  • Antarctic Plate
• Driving Forces


  • Mantle Convection
  • Slab Pull
  • Slab Suction
  • Ridge Push
• Resisting Forces


  • Slab Resistance
  • Collisional Resistance
  • Transform Fault Resistance
  • Drag Force
• Pacific Ring of Fire


  • Frequented by geologic activities and other associated phenomena such as volcanic eruptions, earthquakes, faulting, and tsunamis, among others
  • More than half of volcanoes are here
• Plate Boundaries


  • Divergent Plate Boundary
  • Convergent Plate Boundary
  • Transform Plate Boundary
• Divergent Plate Boundary


  • When two plates move away from each other
  • A gap or rift between plates is created
  • Molten lava or magma move up and fill the gap, cools down, and forms new oceanic crust
  • Create rift valleys on land that causes the land to sink and create a valley, magma from the mantle can rise to the surface, leading to volcanic activity
• Convergent Plate Boundary

  • When two plates slide toward each other and form either a subduction zone (one plate moves underneath the other) or an orogenic belt (the two plates simply collide and compress, region of deformed rocks)
• Types of Convergent Plate Boundaries


  • Oceanic-oceanic
  • Oceanic-continental
  • Continental-continental
• Oceanic-oceanic Convergent Boundary


  • A subduction zone is formed
  • The descending oceanic plate melts upon contact with the asthenosphere
  • The molten material rise and create a chain of volcanic islands
• Oceanic-continental Convergent Boundary


  • The denser oceanic plate goes down beneath the continental plate and melt to form magma
  • Hot and less dense magma will seek a vent, the volcanoes, to reach the surface
  • Also form trenches and volcanic mountains on land
  • Create the strongest earthquakes and tsunamis
• Continental-continental Convergent Boundary


  • No subduction happens
  • The 2 plates compress and crumple, creating highly folded and uplifted mountain ranges
• Transform Plate Boundary


  • Plates horizontally slide against each other in opposite directions
  • No mountains or volcanoes are produced
  • Redistribute stress and accommodates the movement between neighboring plates
  • Earthquakes result from the movement of plates and release massive amounts of energy
• Types of Faults


  • Normal Fault
  • Reverse Fault
  • Strike-Slip Fault
  • Oblique-slip Fault