The main theory believes that there is an uneven distribution of heat in the mantle, caused by heat from the core. Hot mantle material will rise from near the core and sink as it reaches near the lithosphere This motion of hot rising and cold sinking is known as a convection cell

1. Slab Pull When ocean lithosphere is being subducted beneath another plate, if drags the rest of the lithosphere behind is down as well. This slab pull is the downward arm of the convection cell Found at convergent boundaries

2. Ridge Push When oceanic crust is being made at divergent plate boundaries, it is pushing the oceanic lithosphere away from the upwards arm of the convection cell This motion is found at divergent plate boundaries

3. Mantle Plume The rising mantle materials is the up ward arm of the convection cell can happen in a single place in the middle of a plate and create a hot spot/island Example: Hawaii

Shaking of the Earth’s crust Caused by a break or shift in the Earth’s crust Is it possible for an earthquakes to happen in the mantle? _______ Why Not? Mantle is too soft to break or crack The energy that is released when the rocks begin to move is called elastic energy. Think of it like this: when a rubber band is stretched and the tension builds up before it is released

1. Plate boundaries have earthquakes because there are two plates rubbing against each other’s rocks thus creating shockwaves through the crust. 2. All other earthquakes happen at faults, which are ancient plate boundaries or cracks in the Earth that show movement every once in a while.

 Foreshocks  Smaller earthquakes that occur before the big earthquakes Do these always happen? _________ How long before the earthquake do foreshocks happen? Months or days before  Aftershocks  Smaller earthquakes that occur after the big earthquake Why would these cause more damage if they are smaller than the big earthquake? The buildings and foundation were already weakened with damage from the first hit

Focus  Origin point in the earth where the earthquake starts Waves from this will travel in all directions If the focus is shallow underground, meaning it is closer to the surface, it is more dangerous than an earthquake that is deep underground

Epicenter  Location on the Earth’s surface directly above the focus of the earthquake Why do we care more about the epicenter of an earthquake than the we do about it’s focus? It is where all of our possessions are located

The measure of how strong an earthquake is Higher numbers means that the earthquake is stronger

1. Surface Waves  Waves that travel along the Earth’s surface Slowest waves, but they are the strongest of all the waves Most destructive of the earthquake waves Why? Because these waves travel along the surface, it makes us vulnerable Can travel through solids only

Primary Waves (AKA P-waves) These waves will pull and push the ground underneath you Fastest waves, but not the strongest P-waves can travel through solids and liquids Least destructive, but these are the first parts of an earthquake that you’ll feel

3. Secondary waves (AKA S-waves) These waves will cause an up and down motion of the ground Strong waves, but second to the surface waves Slower than p-waves, but faster than surface waves Fairly destructive, definitely more so than the p-waves S-waves cannot travel though air and liquids **Can these waves travel through the outer core?*** ______

Seismogram Paper record of an earthquake You need 3 of these to find an earthquake epicenter Seismograph Instrument that records earthquakes

A mountain that erupts violently, releasing lava, ash, and other hot crustal materials

Magma Chamber  Place where magma is held underground until eruption Conduit (pipeline)  Lava tube that carries magma to surface Vent  Opening at the top that releases the magma

Crater  Depression surrounding the vent that is blown off during eruption Pyroclastics  Molten rock bombs, ash, and other lava fragments released out or off the volcano

1. Plate Boundaries Convergent boundaries will form more violent and explosive volcanoes At divergent boundaries, the volcanoes are less violent and less explosive 2. Hot Spots When weakened lithosphere has allowed mantle material to rise through thus creating islands in the middle of some oceans If they are on continents, they usually create supervolcanoes under the surface

Viscosity  the ability to flow When things flow fast, they have a high viscosity and the lava can move up to 50 mph When things flow slow, they have low viscosity and the lava moves as slowly as in inches per hour Ash and other aerosols can block out the Sun, causing temperatures to drop on a global scale Ash can also combine with rain clouds and produce acid rain Larger pyroclastics called volcanic bombs will destroy property upon impact Lava flows will burn anything they come in contact with until it has cooled enough to become igneous rock

Cinder Cone Shortest on land average 8-10 feet tall Made of only pyroclastics, no lava flows Usually only erupts once in its life time No viscosity Violent for a short period of time Lots of gases released Example: Yellowstone Diagram of Cinder Cone

Composite (Cone) Tallest volcanoes on land Made of lava flows and pyroclastics Erupts very violently Erupts on a scheduled build up ( years) High viscosity means a high silica content to the lava High amounts of gases released Example: Mt St. Helens Diagram of Composite

Shield Volcano Tallest underwater volcano Made of mostly lava flows and maybe a few pyroclastics Erupts often (daily to monthly) Low viscosity which means a low silica content Very few gases are released Example: Hawaii Diagram of Shield