Earthquakes and Volcanoes Review . Describe the following types of plate boundaries, the stress associated with each one of them, and what types of events or features can occur at the boundary:. The three types of boundaries are:
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Describe the following types of plate boundaries, the stress associated with each one of them, and what types of events or features can occur at the boundary:
The three types of boundaries are:
1. Convergent – plates are moving towards one another or colliding (compression) – creates mountains
2. Divergent – plates are moving apart (tension) – creates rift zones
3. Transform – plates are sliding horizontally past one another (shearing) – causes earthquakes
The mid-ocean ridge is a long under-sea mountain chain that forms along the floor of the major oceans. This is usually where new ocean floor is made due to it being a divergent boundary.
Deformation is the change in shape of the land due to pressure being applied.
Deformation is NOT always bad because it does not always lead to destructive results.
Stress is the amount of force per unit area that is placed on a given area or material.
Three types of stress are :
Tension, shearing, compression
When stress is applied to rocks, folding and faulting takes place. This means the rocks bend or break.
1. During compression, rocks are pushed together (convergent boundary) and form mountains.
2. During shearing, rock pushes in different horizontal directions (transform boundaries) causing a rock to thrust or tear apart. This causes earthquakes.
3. Tension is stress that occurs when forces act to stretch an object (divergent boundaries). This can cause sea-floor spreading or rift valleys.
MOST earthquakes occur at tectonic plate boundaries.
A fold when stress is applied to a material and causes the material to bend.
A fault is when stress is applied to a material and causes the material to break.
Faults occur with more stress or faster applied stress while less stress creates folds.
Magnitude is the strength of an earthquake.
Magnitude is determined by the seismic waves that are detected by a seismograph.
Intensity is the amount of damage caused by an earthquake
The scale used to measure earthquake magnitude (strength) is the Richter Scale.
Seismic waves – wave of energy that travels through the earth and away from the earthquake’s focus in all different directions.
Body Waves (P-waves and S-waves) and Surface waves
Continued on next slide……
P-waves are primary waves or the first waves sent out during an earthquake. They are the fastest. **They can travel through solids, liquids, and gases.
S-waves are also called shear waves or secondary waves. They can travel ONLY through solids.
Surface waves are the seismic waves that do the most damage.
The focus is where the earthquake starts in the earth’s body while the epicenter is directly above the focus on the earth’s crust.
To stay save during an earthquake:
1. Crouch down under a table or something sturdy and cover your head.
2. If outside, lie face down with your head away from buildings, power lines, and trees.
3. If in a car, pull over but remain inside.
Earthquakes can not be predicted because seismologists do not know when or where tectonic plates are going to move next.
Most volcanic belts form along tectonic plate boundaries. Many form along the Pacific plate on the ocean floor. However, they also occur at hot spots where magma rises through faults in the earth
Magma is hot, molten rock that is beneath earth’s surface that is pushed upward due to the pressure beneath Earth’s surface and the fact that the magma is less dense.
Groundwater that is heated by magma gets it’s energy from Earth’s core, this is a form of geothermal energy.
The Ring of Fire is a major earthquake and volcano zone that extends nearly all the way around the edge of the Pacific Ocean.
Earthquakes and volcanoes are all due to heat pressure beneath Earth’s surface. They are created when tectonic plates move. They both form new landforms. Energy is associated to both occurring.