Earthquakes and Volcanoes Flashcards
What are the three types of waves?
P waves, S waves, and L waves
Describe P waves:
P waves are the first waves to hit as they travel the fastest. They are a compression wave(push-pull). They travel through all layers of earth(body waves).
Describe S waves:
S waves are the secondary waves and they are the second fastest. They are a shear wave and they move in a up-down fashion. They travel through only solid layers but they are also considered body waves.
Describe L waves:
L waves are the slowest and cause the most damage due to their rolling motion. The are only in the lithopshere so they are considered surface waves. They are the largest.
How do you find the epicenter?
You can use seismometers and three locations and draw a circle around the locations representing the distance from the epicenter. Where the circles intersect is the epicenter.
What is the epicenter?
The epicenter is the point on the surface that feels earthquakes first.
What is the focus?
The point in which the earthquake originates.
What is a normal fault?
A normal fault is a result of tension. They occur near divergent boundaries and the foot wall moves upwards in relation to the hanging wall.
What is the foot wall vs. the hanging wall?
When you have a fault, if you go down from that, you get the foot wall. If you go up from that, you get the hanging wall.
What is a reverse fault? What is a thrust fault?
A reverse fault is a result of compression. It occurs at convergent boundaries and the hanging wall moves up in relation to the foot wall. A thrust fault is where, in a reverse fault, the fault is at a low angle (more horizontal).
What is a strike-slip fault?
A strike-slip fault is a result of shear stress. It happens at transform boundaries and is when two adjacent plates move past each other. If you are facing the other plate and it is moving left, it is a left lateral strike-slip.
Where on a seismograph would you see each type of wave?
The P-wave comes first, then the S-wave, then the L-wave and the seismograph usually works left to right.
What is the S-P interval and how do you measure it?
The S-P interval is the time between the 1st P wave and the first S wave.
What is amplitude?
Amplitude is the height of the biggest S wave.
What is the relationship between silica content and viscosity (explosiveness)?
The more silica, the higher the viscosity.
Why does the same magnitude earthquake cause more damage in one area?
The same earthquake can cause more damage because of population, location, underlying material, building materials and height, duration, and depth of the focus. Also, the earthquake could trigger a landslide and if it is near the coast a tsunami could occur.
What scale measures the damage of an earthquake?
The Mercalli scale, which goes from i to xii.
What is the difference between earthquakes with a magnitude of 3 and 4 in terms of ground-shaking and energy released?
Between every whole number on the Richter scale, there is 10x more ground-shaking and 32x more energy released.
Describe a shield volcano:
A shield volcano is the largest type of volcano. It is wide with a gentle slope. It has very iron-rich magma and basalt forms from its lava. It has “quiet” eruptions and it has multiple vents. It occurs on oceanic crust. An example of a shield volcano is hawaii.
Describe a cindercone volcano:
A cindercone is the smallest volcano as it grows on top/near other volcanoes. It is steep and pointy with one vent and it’s magma is medium silica and has a gassy eruption. Its ash forms tephra. An example of this is the sunset crater.
Describe a composite/stratovolcano:
A stratovolcano is tall and steep and is often snow-covered. It has high silica magma and is viscous. It has layers of either andesite or rhyolite that alternate with tephra. It has lahars an is explosive. It occurs on continental crust. An example of this volcano is Mt. St. Helens.
