Earth Science: Structure of the Earth

Crust

• The outermost layer of the Earth, divided into continental and oceanic crust.

Continental Crust

• Composed mainly of granite, thicker than oceanic crust, less dense than oceanic crust.

Oceanic Crust

• Composed mainly of basalt, thinner than continental crust, denser than continental crust.

Lithosphere

• The rigid, outermost layer of Earth, composed of the crust and the upper mantle.
• It is divided into tectonic plates that move and interact, causing earthquakes and volcanic eruptions.

Asthenosphere

• A soft, partially molten layer of the upper mantle located beneath the lithosphere.
• It is the source of magma for volcanoes and allows the tectonic plates to move.

Convection Current

• The flow of hot, less dense material in the mantle that rises towards the surface, cools, and then sinks again.
• This circular movement drives the tectonic plates.

Mantle

• The thickest layer of the Earth, located between the crust and the outer core.
• Composed mainly of silicate rocks and is mostly solid, with a partially molten layer - the asthenosphere.

Outer Core

• Liquid layer of the Earth, composed mainly of iron and nickel, responsible for Earth's magnetic field.

Inner Core

• Solid, innermost layer of Earth, composed mainly of iron and nickel, extremely hot and dense.

Pangaea

• A supercontinent that existed millions of years ago, containing all of Earth's continents.

Panthalassa (Paleo Pacific)

• The superocean that surrounded Pangaea.

Mohorovicic Discontinuity

• The boundary between the Earth's crust and the mantle, also known as the "Moho".
• Characterized by an abrupt increase in seismic wave velocity.

Gutenberg Discontinuity

• The boundary between the Earth's mantle and the outer core, characterized by a sharp decrease in seismic wave velocity.

Lehmann Discontinuity

• The boundary between the Earth's outer core and the inner core, characterized by a sudden increase in seismic wave velocity.

Seismic Waves

• Vibrations that travel through the Earth, generated by earthquakes, volcanic eruptions, or explosions.
• Used to study the Earth's interior.

Body Waves

• Seismic waves that travel through the Earth's interior.

Surface Waves

• Seismic waves that travel along the Earth's surface.

Alfred Wegener

• A German scientist who proposed the theory of continental drift, suggesting that the continents were once joined together in a supercontinent called Pangaea.

Harry Hess

• An American geologist who proposed the theory of seafloor spreading, suggesting that new oceanic crust is formed at mid-ocean ridges and spreads outward.

Plate Tectonic Theory

• A unifying theory that explains the movement of Earth's lithospheric plates and the associated phenomena like earthquakes, volcanic eruptions, and mountain building.

Earthquakes

• Sudden releases of energy in the Earth's crust, caused by the movement of tectonic plates along fault lines.

Orogenic Belt

• A zone of mountain building, typically found along convergent plate boundaries.

Shear Zone

• A zone of deformation in the Earth's crust, where rocks are subjected to lateral stress, resulting in shearing and faulting.

Orogenesis

• The process of mountain building, involving folding, faulting, and uplift of rocks.

Pacific Ring of Fire

• A zone of intense seismic and volcanic activity encircling the Pacific Ocean, where numerous convergent plate boundaries occur.

PHILVOCS

• The Philippine Institute of Volcanology and Seismology, responsible for monitoring and studying earthquakes and volcanic activity in the Philippines.

Focus (Hypocenter)

• The point within the Earth where an earthquake originates.

Epicenter

• The point on the Earth's surface directly above the focus of an earthquake.

Faults

• Fractures or breaks in the Earth's crust, where movement has occurred.

Intensity

• A measure of the severity of an earthquake's effects at a particular location, based on observed damage and ground shaking.

Magnitude

• A measure of the total amount of energy released by an earthquake, often expressed on the Richter scale.

Horst

• An uplifted block of land between two faults, forming a raised plateau or mountain.

Graben

• A sunken block of land between two faults, forming a valley or basin.

Convergent Plate Boundary

• A boundary where two tectonic plates collide, resulting in mountain building, earthquakes, and volcanic eruptions.
• Subduction zones, where one plate is pushed beneath another, are a common feature of convergent boundaries.

Divergent Plate Boundary

• A boundary where two tectonic plates move apart, forming mid-ocean ridges and rift valleys.
• New oceanic crust is created at divergent boundaries.
• When continental crust diverges, it can lead to rifts forming and eventually splitting the continent into separate landmasses.

Transform Plate Boundary

• A boundary where two tectonic plates slide past each other horizontally, resulting in earthquakes.
• No new crust is created or destroyed at these boundaries.
• The San Andreas Fault in California is a well-known example.

Contraction Theory

• A theory that proposes the Earth is shrinking due to cooling and contraction.
• This theory was once used to explain the formation of mountains, but it is now widely discredited.

Domestic Use

• The use of water for daily activities such as cooking, cleaning, and drinking.

Supercontinents

• Giant landmasses formed by the merging of all or most of Earth's continents.
• Examples include Pangaea, Rodinia, and Gondwana.

Primary Plates (Memorize 6)

• North American Plate: Encompassing North America, Greenland, and parts of the North Atlantic Ocean.
• South American Plate: Encompassing South America and part of the South Atlantic Ocean.
• Eurasian Plate: Encompassing Europe and Asia (excluding India).
• African Plate: Encompassing Africa, Madagascar, and part of the Atlantic Ocean.
• Indo-Australian Plate: Encompassing India, Australia, and part of the Indian Ocean.
• Antarctic Plate: Encompassing Antarctica and surrounding ocean floor.

Secondary Plates (Memorize 6)

• Caribbean Plate: Located between North and South America.
• Cocos Plate: Located off the coast of Central America.
• Nazca Plate: Located off the coast of South America.
• Philippine Plate: Located in the western Pacific Ocean.
• Arabian Plate: Located in the Middle East.
• Scotia Plate: Located near the southern tip of South America.

Evidence of the CDT (Wegener’s Theory)

• Fit of Continents: Continents fit together like puzzle pieces, especially the coastlines of South America and Africa.
• Fossil Distribution: Identical fossils found on different continents suggest a past connection between them.
• Rock Formations: Identical rock layers found on different continents suggest a past connection between them.
• Paleoclimate Data: Glacial deposits found on different continents located in different climates today suggest a past connection.

Seismic Waves

• Primary Waves (P-waves):
  • Compressional waves, traveling through solids, liquids, and gases.
  • Fastest type of seismic waves, arriving first at seismograph stations.
• Secondary Waves (S-waves):
  • Shear waves, traveling only through solids.
  • Slower than P-waves, arriving second at seismograph stations.

Continental Crust

• Thick, less dense, and composed mainly of granite.

Oceanic Crust

• Thin, denser, and composed mainly of basalt.

Aquifer

• A layer of rock or soil that stores groundwater.

Runoff

• The flow of water over the Earth's surface, typically from precipitation.

25%

• Approximately 25% of Earth’s accessible freshwater is groundwater.

Outer Core

• Liquid layer of the Earth, composed mainly of iron and nickel.

Estuaries

• Areas where freshwater rivers meet saltwater oceans.

Potable Water

• Safe drinking water, free of contaminants.

Transpiration

• The process of water moving through a plant and evaporating from its leaves.

Evaporation

• The process of water changing from a liquid to a gas.
• It occurs when liquid water is heated, and it is responsible for the formation of clouds.

Transform Plate Boundary

• A boundary where two tectonic plates slide past each other horizontally.
• It is characterized by earthquakes, but not volcanic activity.

Driving Forces

• Convection Currents: Heat from the Earth’s core creates convection currents within the mantle, which move the tectonic plates.
• Slab Pull: Dense oceanic plates sink into the mantle at subduction zones, pulling the rest of the plate along with them.
• Ridge Push: Newly formed oceanic crust at mid-ocean ridges is raised and pushes the plates away from the ridge.

Resisting Forces

• Basal Drag: Friction between the base of the lithosphere and the asthenosphere.
• Mantle Drag: Resistance from the mantle as it moves the plates.
• Plate Resistance: The internal strength of the plate itself can resist movement, especially in larger continents.

Explore the layers of the Earth, including the crust, mantle, and lithosphere. This quiz covers essential concepts like continental and oceanic crust, tectonic plates, and convection currents. Test your knowledge about the Earth's structure and processes.