Chapters 5, 6, 7 Flashcards
Describe the three types of faults.
Normal fault – two plates are diverging, the foot wall is above the hanging wall.
Reverse Fault- two plates are converging, the hanging wall is above the foot wall.
Strike-slip fault – two plates slip past each other.
Describe the three types of stress that can cause faults.
Tension- pulls out until it is thin in the middle.
Compression- squeezes until folds or breaks.
Shearing- slips past each other.
Describe the speed and types of motion for P waves, S waves, and surface waves.
P waves – compresses and expands the ground like an accordion, fastest wave. ⬅️➡️ ➡️⬅️
S waves – vibrates from side to side or up and down, slower than P waves but faster than surface waves. ⬆️⬇️⬅️➡️
Surface waves – P or S waves that come to the surface, creates the most damage, the slowest wave. ↪️↩️
P waves, S waves, and surface waves are known as _________ waves.
seismic
Ranks the amount of shaking from an earthquake, 12 ranks.
Modified Mercalli scale
Estimates and rates the total energy an earthquake releases, gives magnitude. We use today, 0–9.5 (as high as it needs to go)
Moment Magnitude scale
Rates the magnitude of small earthquakes based on the size of the earthquake’s waves as recorded by seismographs, earliest scale used, outdated.
Richter scale
Seismograph data shows that earthquakes often occur _________.
Along plate boundaries
According to Wegener’s hypothesis of continental drift…..
All the continents were single together and in one continent called Pangea.
What technology was used in the mid- 1900s to map the mid-ocean ridge?
Sonar
Where and how does seafloor spreading occur?
When molten material erupts, cools, and hardens to form a solid strip of rock. Occurs along mid-ocean ridges and deep-ocean trenches.
Mid ocean ridges form the ___________ mountain ranges on Earth.
Largest
In which location would you most likely find volcanoes?
Along the mid-ocean ridge and a plate subducting under another.
What is the main factor that determines if a volcanic eruption will be quiet or explosive?
This silica content
What force causes magma to erupt to the surface?
Dissolved gases that are trapped and create pressure.
If geologists detect many small earthquakes in an area near a volcano, they can infer…
That the volcano is about to erupt.
Oceanic crust near the mid-ocean ridge is _________ than oceanic crust farther away from the ridge.
Younger
If subduction occurs at a slower rate than oceanic crust can be created, the ocean will _________.
Expand
A major volcanic belt known as the ______________ circles the Pacific Ocean.
Ring of Fire
Describe how geologists use seismic waves to locate an earthquake’s epicenter.
If you know when P waves and S waves arrived at a seismograph after an earthquake, you can find the distance from the seismograph to the epicenter and draw circles on a map at three stations and where they connect is the epicenter.
Describe specific landform and fossil evidence that supports the hypothesis that Africa and South America were once joined.
They could fit together, both had folded mountains, Glossopteris fossils, and Mesosaurus fossils that fit together on the edges of the continents.
According to the theory of plate tectonics, explain what causes changes in Earth’s surface.
It states that the Earth’s plates are in a slow, constant motion, driven by convection currents in the mantle, which explains the formation, movement, and subduction of Earth’s plates.
Contrast an island arc and a volcanic island.
An island arc is a string of islands that progresses in age resulting from volcanoes and a volcanic island isn’t related by age.
Describe the three types of volcanoes.
Shield, cinder cone, composite
