earth science exam #2
What is a tsunami and how do they form?
A tsunami is series of extremely long waves caused by a sudden displacement of the ocean they form as a result from an earthquake
Why is ocean crust subducted beneath continental crust at convergent boundaries?
Because oceanic crust is denser
At what type of plate boundary do very large mountains form? Why?
Convergent plate boundary because plate boundaries make a collision and the mountain is made as the crust is compressed, crumpled and thickened
Why do oceans occur where they do?
Divergent boundaries, sea floor spreading, mid ocean ridges form
Volcanoes are most common at which type of plate boundary?
Divergent plate boundary
What causes the sudden release in energy that results in an earthquake, and how is this energy transmitted away from the focus of the quake?
Earthquakes happen when stress on the edge overcomes the friction the energy is transmitted away from the quake because the energy in the waves travel through the earths crust and causes the shaking
Why is the silica content of magma significant for volcanic eruptions?
It controls the rock type that it forms and it controls the relative viscosity of the magma
What is the geologic time scale?
It is a calendar for events in earths history
What are the two types of body waves, and how do they move?
It squishes and stretches the rock that it moves through
Why was continental drift rejected?
It was an inadequate mechanism
What comes out of a volcano during an eruption?
Magma along with carbon dioxide gas and sulfur dioxide gas
What is the driving force for a volcanic eruption?
Magma contains dissolved gases which are the driven forces for an eruption
What determines the amount of damage that a particular earthquake will cause?
Magnitude scale
Why are magnitude scales more commonly used to measure EQ strength than are intensity scales?
Magnitude scales measure what the damage will be and intensity scales try to measure after damage is done its harder because it's hard to see
Why are some volcanoes more explosive than others?
More Si2, magma viscosity
Even though we have no direct physical evidence from deep within the earth, how do we know so much about the properties and composition of the earth's interior?
Observations of surface rocks, data from earthquakes, flow from heat from the interior
What are the two types of seismic waves?
P and S waves
What are the two types of seismic waves, and which type is most destructive?
P waves and S wavers. P waves are more destructive
What are the principles of relative time?
Placing of events in the order which they occurred but not the actual time they occurred
What are the two types of seismic body waves, and which type is transmitted only through solids?
Pwaves and Swaves and Swaves only travel through solids
What aspect of a volcanic eruption can be hazardous to people 10's of km away from the volcano?
Pyroclastic flow
What is the greatest hazard associated with stratovolcanoes, especially for people who live some distance from the volcano?
Pyroclastic flows and lahars
Why do the plates move?
Sea floor spreading
Why do seismic waves travel through some earth materials with higher velocities and through some materials with lower velocities?
Seismic waves travel through denser materials more quickly and travel more quickly with depth this will change due to temperature, structure, and composition
How can a volcanic eruption change climate?
Sulfur dioxide gas causes global cooling and carbon dioxide gas causes global warming
How do we know that the outer core is a liquid?
Swaves do not pass through it but Pwaves do
What two layers, which consist of the outer part of the mantle and the crust, are most involved in plate tectonics?
The lithosphere and the asthenosphere
How do scientists locate the epicenter of earthquakes?
The seismometer shows circles the location where all the circles meet is where the earthquake will be
What is the seismic gap method?
Theory prediction the relative size and frequency of earthquakes depending on other earthquakes in the area
How and where do stratovolcanoes form?
They form on convergent plate boundaries on a subduction zone they form when two plates collide and one piece of crust subducts under the other
What causes the sudden release of energy along a fault that results in an earthquake?
When stress on the edge overcomes the friction
What are the three types of plate boundaries?
divergent, convergent, transform
Our methods of keeping track of time (days, months, years, etc.) are based on what?
metric scale
Why are tsunamis so destructive?
speed and volume
