Volcanoes

Chapter 8 Section 2 Pgs. 219 - 224

How volcanoes form



Fissure conduit

– crack in the crust, where a forms which acts like a pipe magma travels through  Magma is forced upward toward Earth’s surface by denser surrounding rock  Causes an eruption where magma, solids, and gas are spewed out to form cone-shaped mountains



Lava

– magma flowing on Earth’s surface through a vent or opening 

Craters

– circular hole of volcano 

Tephra

– bits of rock or solidified lava dropping from the air 

Reservoir

– where magma is stored  

Summit Vent

– highest point - opening where lava flows

Where Plates Collide

 Volcanoes form by a collision of large plates of crust and upper mantle  Oceanic plate sinks under another plate, rocks melt, forms chambers of magma

Volcanic Risk Maps

 Used to prepare people and visitors about unsafe areas

Volcanic Eruptions

 Violent or quiet  Lava high in silica produces explosive eruptions  Lava high in iron and magnesium produces more fluid eruptions  The amount of water vapor and gases impact eruptions

Shield Volcanoes

 Largest type of volcano  Gently sloping volcano that emits mostly basaltic lava (very fluid) that is long-lasting, gentle eruptions, explosions minimal

Mauna Loa, HI

 Made from 5 shield cones  Largest volcano on Earth – Mauna Loa in Hawaii, 6 miles tall

Cinder Cone Volcanoes

 Smallest volcano, very steep with large craters  Formed by moderate to explosive eruptions of tephra

Cinder Cone Volcano

 Pu ‘ u ka Pele – Hawaii  Mostly found on the sides of shield volcanoes

Composite Volcano

 Steep sides  Formed by alternating layers of violent eruptions of tephra and quieter eruptions of lava

Composite Volcano

 Most active volcano – Mt. St. Helens in the western part of the state of Washington

Extreme Volcanoes

 Largest volcano in the Solar System – Olympus Mons on Mars, 17 miles tall and over 320 miles across.

Questions

     Hawaii is an example of what type of volcano?

What are the three types of material that a volcano can emit?

The eruption of Mount Vesuvius buried what town in 79 A.D.?

How did people die in the aftermath of the famous Mount Vesuvius eruption?

Mount St. Helen’s erupted violently in 1980. On what continent is this volcano found?