61 terms

Unit Three: Earthquakes and Volcanoes Test Review

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What is an earthquake?
Destructive natural disaster caused by a sudden release of energy when rocks under stress suddenly shift.
Where do earthquakes occur?
In the Earth's crust.
What is the focus of an earthquake?
The FOCUS is the location along a fault where the first motion occurs.
What is the epicenter of an earthquake?
The EPICENTER is the point on Earth's surface directly above focus.
What is elastic rebound?
This is the sudden return of rock to undeformed shape.
The pieces separate at weakest point, then rebound.
What kind of energy do the stressed rocks build up before they fracture and cause an earthquake?
Potential energy
What are the two types of earthquakes waves?
Body waves and Surface Waves
Describe Body Waves.
They travel though the earth and start at the focus. P- and S-waves are the body waves
Describe Surface Waves.
They travel on the surface and start at the epicenter. Rayleigh and Love are the surface waves
Which wave type arrives first?
P-waves
Which wave type arrives second?
S-waves
Which wave type arrives last?
Surface waves
Which wave type causes the most damage?
Surface waves
Which wave travels through solids, liquids, and gases?
P-waves
Which wave only travels through solids?
S-waves
How did earthquake waves teach us about the interior of the Earth?
The speed of seismic waves depends on the composition of the material. P-waves travel through solids, liquids, and gases. S-waves only travel through solids. This is how the liquid outer core was discovered.
Why are there "shadow zones" or areas away from an epicenter where earthquakes waves are not felt or recorded?
The liquid outer core deflects p-waves and s-waves cannot travel through it at all.
What is magnitude?
Magnitude measures the strength of an earthquake. It is related to energy released in the earthquake and is determined from measurements on seismographs.
What is intensity?
Intensity measures the strength of shaking produced by the earthquake at a certain location.
What is the Modified Mercalli Scale?
Mercalli Scale is a measurement system that describes the effects of the earthquake and expresses intensity in Roman numerals.
What is the Richter Scale?
The Richter Scale is an older system used in 20th century to measure earthquake magnitude. It was based on ground motion.
What is the Moment Magnitude Scale?
The Moment Magnitude scale is the new system for measuring earthquake magnitude and is more accurate. It is based on the size of the area of the fault that moves, the average distance that the fault block moves, and the rigidity of the rocks in the fault zone.
How deep are the usual earthquakes at transform boundaries?
Only shallow earthquakes (0-70km).
How deep are the usual earthquakes at convergent boundaries?
All earthquake depths (shallow, intermediate, and deep) occur at this boundary type because of the subduction zones.
How deep are the usual earthquakes at divergent boundaries?
Only shallow earthquakes (0-70km).
When locating the epicenter of an earthquake, how many stations' seismograms do you need?
THREE. You need three so that you can calculate the distance and then draw the three circles. Where they intersect is the epicenter.
If you have three stations different distances from the epicenter, which station would experience the earthquake first?
The station that is closest to the epicenter.
If you have three stations different distances from the epicenter, which station would experience the earthquake last?
The station that is furthest away from the epicenter.
Name three hazards associated with earthquakes.
1. Collapse of buildings.
2. Tsunamis
3. Landslides
What is a tsunami?
A gigantic ocean waves caused by severe ground shaking.
What is a landslide?
Seismic waves destabilize cliffs and steep slopes. Rocks and soil fall down slopes.
What is the area around the Pacific Ocean where there are a lot of earthquakes and volcanoes called?
Ring of Fire.
What is a volcano?
A mountain, typically conical, having a crater or vent through which lava, rock fragments, hot vapor, and gas are being or have been erupted from the Earth's crust.
Where do volcanoes form?
Subduction zones, Ocean trenches, Tectonic plate boundaries, Mid-ocean ridges, and at Hot Spots
What is a composite volcano?
A composite volcano is a steep-sided and symmetrical volcano built with layers of lava flows. It alternates between eruptive explosions and quieter lava flows.
What is another name for a composite volcano?
Stratovolcano
What is a cinder cone volcano?
A cinder cone volcano is made from explosive eruptions. It is composed of pyroclastic materials. It has steep sides and a bowl-shaped crater. It is the most common type of volcano.
What is a shield volcano?
A shield volcano is built from fluid lava flows. It has gently sloping sides and a broad base.
What is a Hot Spot?
Hot Spots are areas of volcanism within tectonic plates.
Mantle plumes develop and hot spots form above plumes.
Some not associated with plate boundaries.
What is a vent in a volcano?
Vent - an opening in a volcano connecting the magma to the surface.
Side Vent - magma reaching the surface through another opening.
What is a magma dome or chamber?
Magma Chamber or Dome - large underground pool of molten rock sitting underneath the Earth's crust.
What is the crater of a volcano?
Crater - a bowl shaped area that forms around a volcano's central opening.
What is the conduit or pipe of a volcano?
Conduit or Pipe - the channel from the magma chamber to the vent to bring the magma to the surface.
Where is the lava flow of a volcano?
Lava flow - magma that flows onto Earth's surfaces.
How is magma formed?
Produced by partial melting of Earth's mantle and crust.
What is a caldera?
Large, basin-shaped depression formed by the collapse of a volcanic cone.
What are the most common gases found in magma?
Water vapor and carbon dioxide
Describe Felsic lava.
Felsic lava is:
1. More viscous lava
2. Has a higher silica content.
3. Has more explosive eruptions.
4. Lava flows slower and thicker.
5. Example is A'a lava
Describe Mafic lava.
Mafic lava is:
1. Less viscous lava
2. Has low silica content.
3. The lava tends to ooze out.
4. Lava flow faster and thinner.
5. Example is pahoehoe lava
Describe lava that cools on top of the Earth.
It forms rocks called extrusive igneous that usually cool quickly and have small or no crystals.
Describe lava that cools on inside the Earth.
It forms rocks called intrusive igneous that usually cool slowly and have large crystals.
What are igneous rocks?
Rocks formed from magma (inside the earth) or lava (on top of the earth).
Name three explosive extrusive volcanic rocks.
Pumice, Scoria, and Obsidian
What are some differences between Obsidian and Pumice volcanic rocks?
Pumice - light, gassy with lots of air bubbles - cooler formation temperature - cools quickly
Obsidian - dark, no gas bubbles - hotter formation temperature - cools slowly
Using the Felsic-Volcanic Rock Classification Table in your notes and review sheet for this question: You are holding a felsic volcanic rock in your hand. It has small particle and very few crystals. Name the rock type.
Air Fall Tuff
Using the Felsic-Volcanic Rock Classification Table in your notes and review sheet for this question: You are walking and notice that the volcanic rock pieces are getting smaller. Are you walking toward the volcano or away from it?
Away from it.
Using the Felsic-Volcanic Rock Classification Table in your notes and review sheet for this question: You are holding a felsic volcanic rock in your hand. It has a welded texture and you found it about 15 kilometers from the volcano. Name the rock type.
Air Flow Tuff
What is viscosity?
the resistance of a liquid to flow.
If a liquid does not flow very well, does it have high or low viscosity?
High viscosity
Magma with a higher viscosity contains more of what type of compound?
Silica
Magma with a lower viscosity contains what type of compound?
It contain more iron and magnesium and very little silica.
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