When stress increases on a fault in the rock until it breaks.
What causes and earthquake?
The point in the earth's surface directly above the focus.
What is the epicenter?
The point beneath the earth's surface where the rock first breaks and causes an earthquake.
What is the focus?
They draw a circle around each seismic station and the point where all three intersect is the epicenter.
How to scientists find the epicenter?
Primary waves that compress and expand and can travel through both solids and liquids.
What are P waves?
Secondary waves that vibrate from side to side and cannot go through liquids.
What are S waves?
The most severe seismic waves that occur when P and S waves reach the surface.
What are Surface Waves?
The record of the Earth's seismic waves produced by a seismograph.
What is a seismogram?
A scientist that studies earthquakes.
What is a seismologist?
A device that records ground movements caused by seismic waves as they move through the earth.
What is a seismograph?
It measures the amount an earthquake shakes or can be felt by using twelve categories.
What is the Mercalli Scale?
The magnitude or size of an earthquake is measured on this scale based on the sizes of the recordings on seismographs.
What is the Richter Scale?
This rates the total energy an earthquake releases or the magnitude. It is used more often then the Richter Scale.
What is the Moment Magnitude Scale?
the West Coast, Arkansas, Tennessee, Alaska
Which area in the U.S. are at risk of earthquakes?
Shear Walls, Tension Ties, Base Isolators, Cross Braces, Dampers, Flexible Pipes
What objects can you put in an earthquake safe building?
Bolt the house to concrete foundation, strap the heater to the wall, use metal connections to strengthen the house frame, fasten cabinets to the walls, secure chimneys with metal brackets, remove heavy items from the walls above the beds.
What procedures can you go to to make an earthquake safe house.
A mountain that forms when magma rises to the surface.
What is a volcano?
On convergent and divergent plate boundaries.
Where are volcanoes located?
Magma is a molten mixture of rock, gases, and water.
What is magma?
Lava is magma after it has reached the surface.
What is lava?
Viscosity and silica content
What are the properties of magma?
Earthquakes can cause buildings to fall over and injure people.
What damage can earthquakes cause?
A hot spot is a weak spot in the earth's crust where magma can flow from.
What is a hot spot?
An island arc is when one plate subducts another one and puts pressure on the plate above it which cracks. Through that crack magma flows.
What is an island arc?
On convergent plate boundaries.
Where are island arcs formed?
Hot spot islands can be in the middle of tectonic plates whereas Volcanic belt islands can be only on the boundaries. Hot spot islands don't move, plates move over it.
What is the difference between hot spot islands and volcanic belt islands?
Pahoehoe is freely flowing lava from quiet explosions. When it cools it forms rope-like coils.
What is pahoehoe?
Aa is formed from slow-moving lava that when it cools it forms chunks.
What is aa?
Pyroclastic Flow is lava that is broken into bombs, ash, gases, and cinder.
What is pyroclastic flow?
A caldera is a volcano that has collapsed into a hole after the magma chamber has emptied. The island in the center is the beginning of a new volcano.
What is a caldera?
The magma chamber is pockets of magma beneath the surface.
What is the magma chamber?
The pipe is the long tube that connects the magma chamber to the surface.
What is the pipe?
The central vent is the main vent that releases magma and gas.
What is the central vent?
The side vent is another vent through which magma and gas escapes.
What is the side vent?
Knocks down bridges, buildings, causes avalanches and land slides
What is shaking?
What is liquefaction?
Smaller earthquakes that follow the larger earthquake.
What is an aftershock?
What are tsunamis?
The spread of lava as it leaves the volcano.
What is Lava flow?
The bowl shaped area that forms around the central vent at the top.
What is the crater?
Quiet and explosive
What are the two types of eruptions?
Expels red hot lava, ash, dust, and gas
What is an eruption?
tension (divergent boundaries), compression (convergent boundaries, shearing (transform boundary)
What are the three types of stress?
normal fault (convergent), reverse fault (divergent, and strike-slip fault (transform)
What are the three types of faults?
The hanging wall is the part of the rock that hangs over the fault.
What is the hanging wall?
The foot wall is the part of the rock that sits at the bottom of the fault.
What is the foot wall?
Quiet eruptions have low viscosity and low silica levels.
Describe a quiet eruption.
Explosive eruptions have high viscosity. The silica levels are too high so they get stuck in the pipe. Eventually there is too much silica so it erupts very fiercely.
Describe an explosive eruption.
When a volcano is currently erupting or will soon.
What is an active volcano?
When a volcano is not currently erupting but may in the future.
What is a dormant volcano?
When a volcano is not currently erupting and will most likely not erupt in the future.
What is an extinct volcano?
A batholith forms when a large body of magma cools within the crust.
What is a batholith?
This forms when rock bends as smaller bodies of magma harden and are lifted up towards the surface.
What is a dome mountain?
This is formed when magma hardens within the pipe and soft rock wears away exposing hard volcanic rock.
What are volcanic necks?
These are formed when magma moves across rock layers. It moves horizontally.
What is a dike?
These are formed when magma squeezes in between layers of rock. It moves vertically.
What is a sill?
These form when thin lava flows forms level areas instead of mountains.
What are lava plateaus?
It is caused by expansion of trapped gases which forces it to push the magma out of the chamber, through the pipe, and out the vent.
What causes an eruption.
A wide, gently sloping volcano
What is a shield volcano?
A volcano with a wide crater and a high viscosity that is in the shape of a cone. It is extremely steep and is made from cinders, ashes, and bombs.
What is a cinder-cone volcano?
It is a tall volcano with a small crater and alternating layers of lava and ash. It is made from ash, bombs, cinders, and lava.
What is a composite volcano?
A break in the earth's crust along which rock moves.
What is a fault?