1. Oorogeny & Volcanoes
Isostasy: the equilibrium that occurs with mountain building processes (roots = top)
Oorogeny: a process in which forces and events lead to structural deformation of the crust to form a mountain range.

2. Oorogeny: Mountain Building Processes:
4 types of Mountains:
1. Folded: by compression forces – ex. Himalayas
2. Fault Block: by tension forces – ex. Grand Tetons
3. Volcanic Mountains: by eruption – ex. mountains
in the ring of fire
4. Plutonic: by magma
pushing crust up,
but no lava escapes
– ex. Sierra Nevada’s.

3. A volcano is an opening in Earth’s crust that has released molten rock.
Magma is melted rock below Earth’s crust
Lava is magma that extrudes onto Earth’s surface from a volcanic vent
A vent is an opening in a volcano where lava escapes
Viscosity is a measure of a fluid's resistance to flow The higher the viscosity the slower the fluid flows.
(3 ¼ minute volcano video)

4. 3 types of magma: Basaltic: found in oceanic crust, non-
explosive, low viscosity, less than 50% silica.
2. Andesitic: found at oceanic - continental plate boundaries, explosive, medium viscosity, % - 60% silica.
3. Rhyolitic found in continetal crust, explosive, high viscosity, more than 60% silica.

5. A caldera is a volcanic crater that forms when the summit or side of a volcano collapses into the emptied magma chamber.
Tephra are pieces of solidified lava, rock, and ash thrown into the air during a violent eruption.
A pyroclastic flow is rapidly moving clouds of tephra mixed with hot, suffocating gases.

6. Most volcanoes are found along plate boundaries, the highest density is known as the ring of fire, an area encircling the Pacific Ocean.
A hot spot is a volcano that occurs away from a plate boundary at a thin spot in the lithosphere. (ex. The Hawaiian Islands)

7. 3 types of volcanoes:
1. A shield volcano has broad, gently sloping sides and a near circular base formed from non-explosive (effusive) eruptions 2. A. composite (strato) volcano is formed by layers of hardened chunks of lava from violent (explosive) eruptions alternating with layers of sediment and lava that oozed down slope before solidifying. Very dangerous because they can remain inactive for centuries, then suddenly come back to life. (ex.: Mt. Vesuvius) 3. A cinder cone volcano has steep sides formed quickly when cinder cones are ejected into the air, fall back to Earth and pile up around the vent. Generally small and form on or near large volcanoes.

8. Effects of Volcanoes
1. Harmful: Increases earthquake activity. Destruction to plants, animals & land from lava, gases, explosion, ash, tsunamis, lahars (mudflows with water),etc.
2. Helpful: Enriches soil for farming with minerals such as potassium, phosphorous, etc. Clears land for new growth. Geothermal energy.
(Yellowstone Super Volcano video: 4 minutes)