Plate Tectonics
New sea floor forms as magma rises to Earth's surface and solidifies at a mid-ocean ridge
sea-floor spreading
How does the fossil record support the continental drift theory?
Fossils of the same type are found on continents that were once together.
When Kilauea in Hawaii erupts the lava often covers a large area and ends up in the ocean. This is an example of a/an
non-explosive eruption
What is an earthquake?
the shaking or trembling caused by the sudden release of energy
Seismic sea wave that is sometimes created when an earthquake starts on the ocean floor.
tsunami
What do the stripes in the sea floor illustrate?
The magnetic field has not always pointed North
What is the main idea Alfred Wegner proposed in the “Theory of Continental Drift” that he published in 1915?
The continents were once a single landmass that drifted apart.
Two materials from an explosive eruption are
pyroclastic materials and ash
What is the focus of an earthquake?
place underground where the rocks break producing vibrations
When a slope of earth becomes unstable?
landslide
What observation did Alfred Wegener make that led him to develop the theory of continental drift?
Continents appear to have once fit together.
How does Earth’s geologic record support the continental drift theory?
Continents are all made from the same three types of rock.
What is a volcano?
Areas of earth’s surface through which magma and volcanic gases pass
Pulling or stretching force creates what type of fault?
extension force
What should you do during an earthquake?
drop, cover, and hold on
Scientists knew that Earth was not getting bigger as new crust was formed at the ridges. What did the discovery of oceanic trenches help scientists understand?
That the crust could be created and destroyed.
How did the discovery of sea-floor ridges affect the ability of the scientific community to accept Alfred Wegener’s ideas?
The ridges helped to explain plate movement.
Mt St. Helens erupted in 1980. What type of volcano is Mt. St. Helens?
composite
Pushing something together creates what type of fault
reverse fault
How much stronger is an earthquake with a magnitude of 4 than an earthquake with a magnitude of 2?
100 times
How did Wegener explain rainforest fossils that are now found in arid or cold regions of Earth?
The land they are on was once closer to the equator.
Magma from the mantle rises to the surface, cool and forms new oceanic lithosphere at what boundary?
divergent
Which type of volcano forms when the magma chamber empties and its roof collapses? It often fills with water.
caldera
What measures the amplitude of the waves from an earthquake?
Richter scale
What is the epicenter of an earthquake?
the point of Earth’s surface directly above the earthquake’s focus