MT 5 LT 2

 What are the 3 types of plate boundaries?  What forms at a convergent boundary?  What is a subduction zone?

 Active Volcano – a volcano that has had at least one eruption during the past 10,000 years  Dormant Volcano - an active volcano that is not erupting, but will erupt again  Extinct Volcano – a volcano that has not erupted for at least 10,000 years & not expected to erupt again

 Viscosity- is a substances ability to resist flow how runny the lava is. High viscosity is not runny and low is runny. Depends on the type of substances in it  Lava-magma that reaches earth’s surface melting rock

 Basalt is the type of rock on the bottom of the ocean and what the ocean plates are made of when it comes up as magma and turns into lava it is runny, viscosity is low.  Silica-rocks that make up continental plates magma rises and turns into lava by melting both basalt from ocean plate and silicates from the continental plate over the top. Depending on the ratio of each, the lava has medium to high viscosity, explosive, etc.

 The sudden occurrence when large amounts of ash, gas and lava is released by a volcano Gases include: carbon dioxide and water vapor

Hot spots and Subduction Zones

 Not on a tectonic plates boundary  Caused by the upwelling of deep mantle plumes  Form a chain of hot spot volcanoes when tectonic plate passes over mantle plumes  Dormant when not over mantle plume

 Subduction Zone: When one plate is forced under another The deep plate edge melts Melted rock and gas work its way upward through the top plate  Always active due to the constant upwelling of magma

 Very gentle slopes  Formed out of layers of lava from repeated non-explosive eruptions  Lava is mild and fluid  Over time, lava layers creating the gentle slopes.  CAN form in the middle of a plate over “hot spots” in the mantle

 Tall & Steep sides  Most well known  Gentle broad bases, but extremely steep near the summit.  Explosive eruptions of pyroclastic material followed by quieter outpourings of lava.  Form at Subduction zones (convergent boundaries)  Extremely dangerous  Erupt infrequently

Over the last 10,000 years, Mt. Shasta has erupted on average once every 800 years. During the 3,500 years the volcano has erupted about once every 300 years. The most recent eruption may have occurred in 1786 A.D.

Early sailors mistakenly thought glistening calcite crystals inside the tuff rocks were diamonds, leading to the incorrect name. Diamond Head formed when hot magma rising up a conduit hit ocean water, causing large explosions that threw exploded magma particles (tuff) into a broad ring. **Like ours here in Lindsay-Lindsay Peak

 Kohala is the oldest of the subaerial volcanoes that make up the Island Of Hawaii. Kohala is considered to be extinct because it has not erupted for 60,000 years.