Boundaries
What do we call a place where two plates slide past each other?
transform plate boundary
What theory states that pieces of Earth’s lithosphere are in constant, slow motion?
plate tectonics
Who proposed the continental drift hypothesis that preceded plate tectonics? (Last Name is required)
Alfred Wegner
What is the topographic feature on the ocean floor formed from sediment buildup called?
abyssal plain
What is any trace of an ancient organism preserved in rock called?
fossil
What boundary type forms when two pieces of continental crust collide and produce a mountain range?
convergent
What is the process called when molten material rises from the mantle and erupts at a mid-ocean ridge to form new oceanic crust?
sea-floor spreading
What type of evidence was NOT used by Alfred Wegener to support his continental drift hypothesis?
human remains, animal fossils, or glacial grooves
human remains
What rock makes up much of the oceanic crust and forms when lava hardens?
Basalt
What name is given to the supercontinent that existed millions of years ago?
Pangaea
What boundary type forms where two plates move away from each other, often creating mid-ocean ridges?
divergent
What is the name of the part of the mantle where convection currents occur and is soft rock that bends like plastic?
asthenosphere
What feature on the sea floor provides evidence that Earth’s magnetic field has changed directions over time?
Magnetic stripes (patterns of normal and reversed magnetic polarity on either side of mid-ocean ridges)
Which type of crust is denser? Explain why.
oceanic crust is denser because it is under immense pressure from the water above
What is the element found in oceanic crust that is oriented (lined up) according to Earth's magnetic field
Iron
Which layer is broken into sections called plates that move on top of the asthenosphere?
lithosphere
What process do most geologists think causes the movement of Earth’s plates?
convection currents in the mantle
What is a magnetic reversal?
A magnetic reversal is an event that causes Earth's magnetic field to reverse direction
Are mid-ocean ridges found in one ocean or all of Earth's oceans?
All of Earth's oceans
How can fossils help scientists know that continents were once joined? Explain
Matching fossils found on different continents indicate the continents were once connected, allowing organisms to live across the joined land.
Why might earthquakes occur at a transform boundary? (Explain briefly.)
the plates briefly get stuck and then release, which causes earthquake waves
Explain how sea-floor spreading adds new crust to the ocean floor along mid-ocean ridges.
Molten material rises at the ridge, creates new crust that pushes older crust away on both sides, continually adding new oceanic crust.
List at least three types of evidence that were used to establish the continental drift theory
continents seem to fit together, similar fossils on different continents, similar land features on different continents and evidence of different past climates (glaciation)
What happens to oceanic crust at a deep-ocean trench?
Subduction — the oceanic crust sinks beneath the trench back into the mantle and is recycled
Briefly explain how magnetic stripes on the sea floor and seafloor spreading together support the theory of plate tectonics.
As molten rock at a mid-ocean ridge cools, magnetic minerals align with Earth's magnetic field. Periodic magnetic reversals create matching stripes of normal and reversed polarity on both sides of the ridge; these stripes and the pattern of ages of seafloor show new crust forms at the ridge and moves outward