Tectonic Plate Boundaries and Earthquakes
What is the best indicator of where earthquakes will happen in the future?
Areas that experienced earthquakes in the past will likely experience earthquakes again.
Describe what causes an earthquake.
As two plates move past one another, the plates can get stuck and stop moving. Stress builds up where the plates are stuck until they eventually break and suddenly move apart, resulting in a rapid release of energy as earthquakes
What are the 4 types of plate boundaries?
1) Divergent, 2) Convergent (Oceanic-Continental), 3) Convergent (Continental-Continental), and 4) Transform
What does the word tectonic mean?
It describes the forces that shape Earth's surface and the rock structures that form as a result.
Describe the modified Mercalli scale.
It measures earthquake intensity based on descriptions of the earthquake's effects on people and structures.
What type of forces happen at a divergent boundary?
Tension
What is the theory of plate tectonics?
That Earth's surface is made of rigid slabs of rock, or plates, that move with respect to each other.
Describe the moment magnitude scale.
A magnitude scale measures the total amount of energy released by the earthquake.
Describe the Richter scale.
A magnitude scale uses the amount of ground motion at a given distance from an earthquake to determine magnitude.
Where is the energy from an earthquake the strongest on the Earth's surface?
At the epicenter.
What type of forces happen at a convergent boundary?
Compression
What land features form as a result of a divergent boundary?
In ocean = mid-ocean ridge; on a continentent = rift valley
Where could you find a divergent boundary?
In the ocean or on a continent
What are the 3 types of seismic waves?
P-wave (primary), S-wave (secondary), Surface waves.
What are the 3 types of scales used to describe earthquakes?
Richter, moment magnitude, and modified Mercalli scales.
What do scientists use to map the layers of the earth?
Seismic waves
Who studies earthquakes?
Seismologists
What type of forces happen at a transform boundary?
Shear
What are the 3 types of faults?
Strike-Slip - blocks of rock move horizontally past each other; Normal - As two blocks of rock diverge, one block of rock moves down relative to another; Reverse - As two blocks of rock converge, one block of rock moves up relative to the other.
Describe subduction.
Subdiction happens at a oceanic-continental convergent boundary where the oceanic plate slides underneath the continental plate.
What is the place called where subduction takes place?
Subduction Zone
What layer of the earth do the tectonic plates "float" on top of?
The asthenosphere which is semi-plastic.
What is the place called where rocks first begin to break and move resulting in an earthquake?
The focus
What layer of the earth are these plates that move?
The lithosphere, which is made up of the crust and the uppermost mantle.
What is the epicenter of an earthquake?
The location on Earth's surface directly above the earthquake's focus.
How do compression forces affect the lithosphere?
They thicken it.
How do tension forces affect the lithosphere?
They thin it.
Are mountains still being formed?
Yes, for example, the Himalayas grow a few millimeters each year due to compression.
What is a split or crack in the Earth's crust called?
a fault
What is a place called where there are many faults?
a fault zone
Where do most earthquakes occur?
along active plate boundaries; in the oceans and along the edges of continents.
Where could you find a transform boundary?
at the edge of two plates, usually an oceanic plate and a continental plate.
What land features form as a result of a transform boundary?
faults and earthquakes
Describe tension forces.
forces that are pulling apart
Describe compression forces.
forces that are squeezing or pushing together
What land features form as a result of a convergent (oceanic-continental) boundary?
in the ocean = deep ocean trench; on land = volcanoes
What land features form as a result of a convergent (continental-continental)boundary?
mountains
What type of motion happens at a divergent boundary?
moving away or separating
What type of motion happens at a transform boundary?
moving past each other or sliding in opposite directions
What type of motion happens at a convergent boundary?
moving towards or collision
Describe shear forces.
parallel forces that act in opposite directions next to each other.
What instrument do scientists use to measure and records ground motion and determine the distance that seismic waves travel.
seismometer
What is convection?
the circulation of material caused by differences in density. The difference in density is caused by the difference in temperature.
What is a seismic wave?
the energy released (vibrations) as a result of rock movement and rocks breaking along faults.
What are earthquakes?
the vibrations in the ground that result from movement along breaks in Earth's lithosphere, called faults.
What method do scientists use to locate an earthquake's epicenter?
triangulation
Where could you find a convergent (oceanic-continental) boundary?
where an ocean and a continent meet (shore)
Where could you find a convergent (continental-continental) boundary?
within a continent
