Illustrate the creation and changing of landforms that have occurred through geologic processes (including volcanic eruptions and mountain-building forces).

Essential to know: the landforms of Earth can be created or changed by volcanic eruptions and mountain-building forces.

• Volcanic eruptions are constructive in that they add new rock to existing land and form new islands, sometimes provide fertile soil, can be used for geothermal energy, and have contributed to the building of our atmosphere. 

• Volcanic eruptions can be destructive when an eruption is explosive and alters/changes the landscape of and around the volcano.

• Magma from the mantle rises to Earth’s surface and flows out an opening called a vent.

• Magma that reaches Earth’s surface is known as lava.

• Viscosity can be defined as internal resistance to flow.

• Viscosity can be affected by temperature or composition.

• Two important components of the composition of magma that affect viscosity are gas content and silica (coming from silicate minerals such as quartz) content.

• The viscosity of magma or lava determines the type of eruption - explosive (like Japan) or effusive (like Hawaii).

• The viscosity of magma or lava can determine the type of volcano that is formed - shield or composite/strato (these are the only two we've studied).

• Volcanoes can be formed in many ways.   a) hot spots form volcanoes in chains as the lithosphere moves over the hot spot, b) volcanoes form when the crust tears open (shield volcanoes), c) volcanoes form when crust is subducted under other crust.

• Be able to Identify locations of shield or composite/strato volcanoes.

· Forces, or stresses, that cause rocks to break or move are:

o Tension—forces that pull rocks apart

o Compression—forces that push or squeeze rocks together 

o Shearing—forces that cause rocks on either side of faults to push in opposite directions

· Forces or stresses (for example, tension and compression) on rocks in the lithosphere can cause them to bend and stretch.

o This bending and stretching can produce mountain ranges.

o If pressure is applied slowly, folded mountains form.

· Forces or stresses (for example, tension, compression, or shearing) great enough to cause

rocks to break can create faults. Faults are places in Earth where the rocks break. Movement occurs when the rock breaks.  Movement will likely occur again in the same places. There are

three types of faults:

o Normal fault – caused by tension forces

o Reverse fault – caused by compression forces

o Strike-slip fault – caused by shearing forces  (A famous, huge, series of strike-slip faults is located in California - The San Andreas Fault.)

· If normal faults uplift a block of rock, a fault-block mountain forms.