VOLCANOES

Most Active Volcanoes

More than 600 active volcanoes on Earth Kilauea in Hawaii erupts continuously. Iceland is a country that is made entirely

from volcanoes.

Effects of Eruptions Volcanic ash and debris can

Kill crops and forests Kill people Destroy habitats

Sulfuric acid from volcanic gases mixes with water vapor to create acid rain. Gases and ash particles can block

sunlight from entering Earth’s atmosphere lowering the overall temperature of the planet. Watch this pyroclastic flow from Mt.

Unzen, Japan: http://www.youtube.com/watch?v=Cvjwt9nnwXY

Human and Environmental Impacts

Soufriere Hills, Montserrat 1995 Volcanologists

knew it was about to erupt.

Some folks refused to leave.

Pyroclastic flows wiped out cities and towns in its path, killing 20 people who ignored the evacuation order.

Volcanoes Plates moving apart—divergent boundaries

Iceland’s volcanoes emerged from seafloor spreading

Eyjafjallajökull eruption 2010 http://www.youtube.com/watch?v=tGPD_0SCDp4

Plates moving together—convergent boundaries Soufriere Hills, Montserrat 2007

http://www.youtube.com/watch?v=8sPyyHY57H4

Hot Spot Volcanoes Hawaii’s Kilauea is the most active volcano in

the world. http://www.youtube.com/watch?v=488BkTUsMa4

How the Hawaiian Islands Formed

Over a period of about 5 million years, the Pacific plate has moved over a hot spot where mantle material is particularly hot and blasts through Earth’s crust like a torch.

The lava that leaks out at the hot spot built up and formed a volcanic island.

As the plate moves over the hot spot, the magma punches through a new spot in the crust, forming new islands.

Volcanoes that are no longer over a hot spot become dormant or extinct.

The volcanic islands that are quiet begin to erode by the ocean waves.

Hawaiian Islands

Older

Newer

Kilauea

Kilauea at Night

Kilauea Lava Tube

Subduction Zone Volcanoes(convergent plate boundaries)

An oceanic plates subducting under another oceanic plate will create an island arc.

An oceanic plate subducting beneath a continental plate will create coastal volcanoes.

Subduction Zone Volcanoes(convergent plate boundaries)

VOLCANIC NECK

Shiprock, New Mexico

DIKES NEAR SHIPROCK

Devil’s Tower, Wyoming, a Volcanic Neck

Volcanic Dike near Devil’s Tower

Volcanic Dike near Devil’s Tower

Another View of the Volcanic Dikes

Another View of the Volcanic Dikes

Volcanic Sill

Granitic Batholiths Exposed!

Yosemite Park,California

Formation of a Caldera

Colorado’s Volcanic Past

The Fish Canyon eruption in southwestern Colorado about 28 million years ago erupted more than 5,000 km3 (3,107 miles3) of magma from the La Garita caldera. That is enough magma to bury the entire state of California to a depth of nearly 39 feet.

Colorado has at least nineteen calderas including one of the world’s largest, the La Garita Caldera. It is so large (22 by 47 miles) that for a long time it was hard for geologists to realize that they were mapping in a giant caldera.

More on La Garita

The scale of La Garita volcanism was far beyond anything known in human history. The resulting deposit, known as the Fish Canyon Tuff, has a volume of approximately 5,000 cubic kilometers (1,200 cu mi), enough material to fill Lake Michigan (in comparison, the May 18, 1980 eruption of Mt. St. Helens was only 1.2 cubic kilometers (0.3 cu mi) in volume).

La Garita Caldera

Crater Lake, Oregon Crater Lake formed around 5,677 (±

150) BC when Mount Mazama exploded.

Crater Lake is the deepest lake in the Western Hemisphere and the third deepest in the world.

Its deepest point has been measured at 1,949 feet.

Crater Lake and Wizard Island

Geologic Map of Mt. Mazama