Plate Boundaries
What type of plate boundary occurs where two plates move apart from each other?
Divergent boundary.
What causes most earthquakes (what happens between plates)?
Sudden release of energy when rocks along a fault slip due to plate movement.
Name one piece of evidence that Alfred Wegener used to support continental drift.
Fossil and rock similarities across continents (e.g., Mesosaurus fossils in South America and Africa), or matching coastlines.
What feature is typically created at divergent boundaries under the ocean?
Mid‑ocean ridge.
Define the word "mantle" in a single sentence.
Mantle: The thick layer of hot, solid rock between Earth's crust and core.
What type of plate boundary occurs where two plates move toward each other and one plate is forced under another?
Convergent boundary with subduction (oceanic–continental convergent).
Which type of plate boundary is most commonly associated with powerful, deep earthquakes?
Convergent boundaries (especially subduction zones) produce powerful, deep earthquakes.
How do matching rock types and mountain chains across continents support plate tectonics?
Identical rock layers/mountains indicate they were formed together before continents separated.
What mountain range formed mainly by the collision of two continental plates?
Himalayas (or Appalachian Mountains in earlier contexts).
What is "lithosphere"?
Lithosphere: The rigid outer shell of Earth, including the crust and the uppermost mantle, broken into tectonic plates.
What type of plate boundary occurs where two plates slide past each other horizontally?
Transform boundary (strike‑slip)
Explain the process by which magma reaches Earth's surface to form a volcano.
Magma rises through the crust and erupts through vents as lava, ash, and gases.
Explain how sea-floor spreading creates new crust.
As magma is forced up through the newly formed gaps in the plate it cools and thus forms new crust.
What kind of landform forms when an oceanic plate subducts under a continental plate?
A volcanic mountain range and an ocean trench (e.g., Andes and the Peru–Chile Trench).
Define "subduction".
Subduction: The process where one tectonic plate sinks beneath another into the mantle.
Name one major mid‑ocean ridge formed at a divergent boundary
Mid‑Atlantic Ridge (one correct example).
Why do subduction zones often create volcanic arcs on the overriding plate?
Subducting oceanic plate melts, forming magma that rises to create volcanoes on the overriding plate.
How do fossil distributions across different continents support the idea that continents were once connected?
Same fossils found on now‑separated continents imply those continents were joined (e.g., Glossopteris).
How are island arcs formed? Give one example.
Island arcs form from volcanism above a subducting plate; example: the Japanese islands or the Aleutian Islands.
What does "seafloor spreading" mean?
Seafloor spreading: The formation of new oceanic crust at mid‑ocean ridges as plates move apart.
Explain how the movement at a convergent boundary between two continental plates differs from a convergent boundary between an oceanic plate and a continental plate.
Continental‑continental convergent: collision and mountain building (e.g., Himalayas); oceanic‑continental: subduction of the denser oceanic plate beneath the continental plate causing volcanic activity and trenches.
Describe how the location of the Pacific "Ring of Fire" relates to plate boundaries and seismic activity.
The Ring of Fire circles the Pacific Ocean where many plate boundaries (convergent and transform) create frequent earthquakes and volcanoes.
Describe how GPS measurements can be useful to directly observe plate movement.
GPS measures plate movement.
Describe how a transform boundary can reshape the landscape over time (give a specific example if possible).
Transform boundaries cause strike‑slip faulting and linear valleys, offset streams, and earthquakes; example: San Andreas Fault creating lateral displacement and fault‑line valleys.
Explain what "convection currents" in the mantle are and how they relate to plate motion.
Convection currents: Circular movements of heated material in the mantle that transfer heat and can drag tectonic plates; mantle material heats, rises, cools, and sinks, creating motion.