NON-EXPLOSIVE ERUPTIONS Non-explosive eruptions are the most common type of eruptions. These eruptions produce relatively calm flows of lava. Non-explosive eruptions produce large amounts of lava.

EXPLOSIVE ERUPTIONS Explosive eruptions are much rarer than non- explosive eruptions. Explosive eruptions are incredibly destructive releasing clouds of hot debris, ash and gas rapidly shooting out of the volcano. Instead of lava flow, explosive eruptions cause molten rock to be blown into tiny particles that harden in the air. An explosive eruption can also blast millions of tons of lava and rock from a volcano.

Volcanic Fragments Volcanic Dust- less that 0.25 mm in diameter (flour) Volcanic Ash- more than 0.25 less than 5 mm (rice) Volcanic Bombs- few cm to several meters. Cinders- volcanic bombs the size of golf balls

What Erupts from a Volcano Magma erupts as either lava or pyroclastic material Lava- is liquid magma that flows from a volcanic vent Pyroclastic material- forms when magma is blasted into the air and hardens.

Types of Pyroclastic Material Volcanic bombs- large blobs of magma that hardens in the air. Lapilli- means “little stones” are pebble like bits of magma that hardens before they hit the ground. Volcanic ash- forms when the gases in stiff magma expand rapidly and the walls of the gas bubbles explode into tiny glasslike slivers. Volcanic blocks- the largest pieces of pyroclastic material which are pieces of solid rock erupted from volcanoes.

Pyroclastic Flows Pyroclastic flows are a dangerous type of volcanic flow that produces an enormous amount of hot ash, dust, and gases that are ejected from a volcano. Pyroclastic flows can race downhill at speeds of 200km/hr or faster. (faster than hurricane winds) The temperature of pyroclastic flows can exceed 700 degrees C.

Where Volcanoes Form A large number of volcanoes lie directly on tectonic plates boundaries. In fact, the plate boundaries surrounding the Pacific Ocean have so many volcanoes that the area is called the ring of fire.

Ring of Fire

Zones There are 3 zones: Ring of Fire- Extends nearly all the way around the edge of the Pacific Ocean Mediterranean Sea- Italy, Greece, Turkey Iceland and Atlantic Ocean- Mid Atlantic Ridge

Volcanic Terminology Volcanic Landforms Crater- funnel shaped pit, or depression at top of volcano Caldera- when a crater becomes too large, it collapses: also can form when the top of a volcano collapses or explodes Lava plateau- is a landform that resulted from repeated eruptions of lava spread over a large area. Ex- Columbia River Plateau Dormant- sleeping volcano Extinct- not known to have erupted in modern history Active- Erupts fairly regularly Hot spots- Volcanically active places on the Earth’s surface that are far from plate boundaries