Earth's Layers, Plate Tectonics, Plate Boundaries, and Plate Movements
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A comprehensive set of Q&A flashcards based on the lecture notes covering Earth's layers, plate tectonics, plate boundaries, and mechanisms of plate movement.
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52 Terms
What is the crust?
The thinnest and outermost layer of the Earth.
What is continental crust?
Thicker but less dense than oceanic crust.
What is oceanic crust?
Thinner but denser than continental crust.
What is subduction?
The sinking or plunging of one plate beneath another due to density.
What percentage of Earth's volume does the mantle occupy?
About 80%.
What is the mantle?
The layer beneath the crust composed of hot molten material.
What is a mantle plume?
A column of rising magma from deep within the mantle.
What is the lithosphere?
The outermost shell of the Earth, including the crust and the upper mantle.
What is the asthenosphere?
The softer, lower part of the mantle that can flow; convection occurs here.
What is the Moho (Mohorovičić) discontinuity?
The boundary between the crust and the mantle.
What is the Gutenberg discontinuity?
The boundary between the mantle and the outer core.
What is the outer core made of?
Liquid iron.
What is the inner core made of?
Solid iron.
What is the Lehmann discontinuity?
The boundary between the outer and inner core.
What is plate tectonics?
The movement of the Earth's lithospheric plates.
What is a tectonic plate?
A piece of the lithosphere.
How fast do plates move according to plate tectonics theory?
A few centimeters per year.
What geological features are associated with plate tectonics?
Trenches, mountains, mountain ranges, volcanoes, rift valleys, ocean ridges.
What geological events are associated with plate tectonics?
Earthquakes, volcanic eruptions, tsunamis.
What is the Pacific Ring of Fire?
A belt around the Pacific where most earthquakes, volcanoes, and mountains occur at plate boundaries.
What is a plate boundary?
The lines at the edges of the lithospheric plates.
What causes plate movement?
Convection currents in the mantle.
What is a convergent boundary?
Where two plates collide.
What geological features form at convergent boundaries?
Trenches, mountains, volcanic arcs.
What is a trench?
A deep underwater trough formed at subduction zones.
What is a volcanic arc?
A curve of volcanoes formed at a convergent boundary (continental volcanic arc or island arc).
What is a continental volcanic arc?
A chain of volcanoes formed by subduction of an oceanic plate beneath a continental plate.
What is a volcanic island arc?
A chain of volcanoes formed by subduction of an oceanic plate beneath another oceanic plate.
What happens at oceanic-continental convergent boundaries?
Subduction occurs; trenches and volcanoes form (continental volcanic arcs).
What happens at oceanic-oceanic convergent boundaries?
Subduction forms trenches and island arcs; volcanoes may develop.
What happens at continental-continental convergent boundaries?
No subduction; mountains are formed.
What is a divergent boundary?
Plates move apart.
What features form at divergent boundaries?
Rift valleys and mid-ocean ridges; seafloor spreading.
What is a rift valley?
A vertical trench that may extend deep into the crust.
What are mid-ocean ridges?
Undersea mountain ranges where seafloor spreading occurs.
What is seafloor spreading?
New ocean floor is created as plates move apart.
What are the geological events at divergent boundaries?
Earthquakes, volcanic eruptions, tsunamis.
What is a transform fault boundary?
Where plates slide past one another (e.g., San Andreas Fault).
What is an epicenter?
The point on the Earth's surface directly above the earthquake's focus.
What is the focus of an earthquake?
The location within the Earth where the earthquake originates.
What is the Philippine Mobile Belt?
A geologic region in the Philippines; many islands originated geologically from oceanic-oceanic convergence or subduction.
Where do many Philippine islands originate geologically?
From oceanic-oceanic convergence; some from subduction.
What is the Continental Drift Theory?
The idea that continents drift slowly over time; proposed by Alfred Wegener; Pangaea was an ancient supercontinent.
Who proposed the Continental Drift theory?
Alfred Lothar Wegener.
What does the term Pangaea mean?
All Earth.
What is evidence for continental drift?
Continental fit; rock formations and glacier scars; coal deposits and ancient climates; fossils like Mesosaurus, Cynognathus, Lystrosaurus, Glossopteris.
What is the Seafloor Spreading Theory?
The ocean floor moves apart; mid-ocean ridges are sites of younger rocks with older rocks farther away.
What is magnetic reversal?
Earth's magnetic field has reversed polarity many times; reversals last less than ~200,000 years.
When was Plate Tectonics Theory developed?
In the 1960s; it posits that the lithosphere is broken into moving plates.
What drives mantle convection?
Heat from radioactive decay in the core and mantle causes hot material to rise and cool material to sink.
What is the asthenosphere?
A soft, less rigid part of the mantle on which lithospheric plates float and move.
What are Ridge Push and Slab Pull?
Ridge Push: gravitational sliding from elevated mid-ocean ridges; Slab Pull: the sinking of a dense subducting plate pulls the rest of the plate downward.