Tectonic Plates and Boundaries Quiz

Earth's Interior

• Earth's main layers are the crust, mantle, and core.
• The layers of the Earth are similar to the layers in a hard-boiled egg.
• The crust is 5-70 km thick.
• The mantle is 2,867 km thick.
• The outer core is 2,266 km thick.
• The inner core is 1,216 km thick.

Studying Earth's Interior

• Scientists study Earth's interior by recording seismic waves (P-waves and S-waves) from earthquakes.
• P-waves travel through both solids and liquids, while S-waves only travel through solids.
• Seismic shadow zones reveal the composition and state of Earth's interior layers.

Layers of the Earth

• Lithosphere: Includes the crust and the solid, rocky part of the upper mantle. This forms the tectonic plates.
• Asthenosphere: The material the tectonic plates float on, semi-molten part of the upper mantle.
• Mantle: Made of molten rocks (magma), 1,600-4,000 degrees Fahrenheit. It makes up 80% of Earth's volume.
• Outer Core: Molten metals (nickel and iron), 4,000-9,000 degrees Fahrenheit.
• Inner Core: Solid metals (nickel and iron), 9,000 degrees Fahrenheit.

Oceanic Crust vs. Continental Crust

• Oceanic crust is typically denser and thinner than continental crust.
• Oceanic crust is composed of basalt.
• Continental crust is composed of granite.
• When they collide, oceanic crust usually sinks below continental crust.

Convection and the Mantle

• Convection is one of the Earth's heat transfer methods.
• Convection currents in the mantle are caused by hotter material rising and cooler material sinking.
• This movement is due to differences in density.

Wegener's Continental Drift

• Wegener's hypothesis proposed that the continents were once joined together in a supercontinent called Pangaea.
• Pangaea then broke apart and the continents drifted to their present locations.
• Evidence supporting continental drift includes the fit of continents, fossil evidence, and geologic rock and sediment comparisons.

Evidence for Continental Drift

• The continents fit together like pieces of a puzzle.
• Similar fossils of plants and animals have been found on continents now separated by vast oceans.
• Matching rock formations and mountain ranges across different continents.

Pangaea

• Pangaea was a supercontinent that existed more than 2,080 million years ago.
• Pangaea broke apart to form the continents we know today.
• Pangaea was surrounded by a large ocean called Panthalassa.
• The supercontinent eventually broke into Laurasia (North) and Gondwana (South).

Theory of Plate Tectonics

• The theory of plate tectonics explains the formation, movement, and subduction of Earth's plates.
• This process is a very slow, gradual process that happens at a rate of approximately 2 cm per year.

Plate Boundaries (Divergent)

• Divergent boundaries are where tectonic plates move apart.
• Molten magma rises to the surface, creating new crust.
• Seafloor spreading is a key process at divergent boundaries (mid-ocean ridges), where the new crust forms.
• Rift valleys are deep valleys formed by diverging plates, an example is the East African rift valley.

Plate Boundaries (Convergent)

• Convergent boundaries are where tectonic plates collide.
• There are three variations: Oceanic-Continental, Oceanic-Oceanic, Continental-Continental
• Oceanic-Continental: Oceanic crust subducts below continental crust, leading to volcanic activity.
• Oceanic-Oceanic: Denser oceanic plate subducts, forming a volcanic island arc.
• Continental-Continental: Collision results in large mountain ranges (e.g., Himalayas).

Plate Boundaries (Transform)

• Transform boundaries are where plates slide past each other.
• This movement doesn't create or destroy crust.
• Earthquakes are common along these boundaries (e.g., San Andreas Fault).
• Faults are fractures in the Earth's crust where rocks have moved relative to each other.

Volcanic Hot Spots

• Hot spots are areas in the mantle where unusually high temperatures cause magma to rise.
• These hot spots often form volcanic landforms far from plate boundaries.
• Hot spots are typically stationary, and as tectonic plates move over them, a chain of volcanoes is created.
• Yellowstone is an example of a hot spot.

Ring of Fire

• The Ring of Fire is a horseshoe-shaped zone of active volcanoes and frequent earthquakes around the Pacific Ocean.
• The volcanoes are associated with convergent plate boundaries.