Over 1500 Active Volcanoes in the World

Over 600 Have Erupted in the last 50 Years.

New Land Forming

• Magma – Molten rock beneath the surface.

(Mafic – dark ocean crust & Felsic – Light continental crust.)

• Lava – Molten rock on the surface.

• Volcanism – The movement of magma to the earth’s surface.

• Volcano – The vent on the earth’s surface through which gases and magma are released.

• Subduction Zones When one tectonic plate moves

under another.

• Mid-Ocean Ridges The largest amount of magma

comes to the surface where plates come apart at mid-ocean ridges.

• Hot Spots Volcanically active area

of Earth’s surface, commonly far from a plate boundary.

An Island Arc form when two ocean plates form a convergent plate boundary.

Indonesia

Life Cycle of an Island formed by a Hot Spot

Volcanoes of Iceland

• Steep slopes.

• Explosive eruptions.

• Pyroclastic material forms the cone.

• Broad at the base with gently slopping sides.• Layers of hardened lava from quiet eruptions slowly

build up the cone.

• Large Volcanic Mountains.

• Alternating Layers of lava flows and pyrocastic material.

• Quiet or Explosive.

At 8:32 Sunday morning, May 18, 1980, Mount St. Helens erupted. Shaken by an earthquake measuring 5.1 on the Richter scale, the north face of this tall symmetrical mountain collapsed in a massive rock debris avalanche. Nearly 230 square miles of forest was blown down or buried beneath volcanic deposits. At the same time a mushroom-shaped column of ash rose thousands of feet skyward and drifted downwind, turning day into night as dark, gray ash fell over eastern Washington and beyond. The eruption lasted 9 hours, but Mount St. Helens

and the surrounding landscape were dramatically changed within moments. In 1982, the President and Congress created the 110,000-acre National Volcanic Monument for research, recreation, and education. Inside the Monument, the environment is left to respond naturally to the disturbance.

http://www.fs.fed.us/gpnf/volcanocams/msh/

Mount St. Helens Blows Smoke on October 1st After Eighteen Years Rest                                                                                                                               

For days the mountain rumbled. And then today, on Friday, October 1st, 2004 at approximately 12:04 Pacific Daylight Time (3 pm EDT) and at 15:14 (6 pm EDT), Washington's Mount St. Helens erupted steam and ash after an eighteen year slumber. The 8,364-foot volcano is located in Kelso, Washington about 30 miles south of Seattle.It is part of a volcanic "ring of fire" so vast that it encircles the Pacific Ocean.