6th Grade Ch. 3 Sec. 1 Volcanoes and Plate Tectonics

Ch. 3 Ch. 3 Sec. 1 Volcanoes & Sec. 1 Volcanoes &

Plate TectonicsPlate Tectonics

• weak spot in crust where molten material comes to surface

http://www.youtube.com/user/NyeTunes#p/u/89/HUCBf058hoA

magmamagma•molten rock from mantle beneath Earth's surface

lava• magma that

reaches surface

http://www.youtube.com/watch?v=K9iZd6wzlCk&feature=related

pillow lava

lava entering the ocean

buried road in Hawaii

After lava has cooled, it After lava has cooled, it forms solid rock.forms solid rock.

• Although you might not wish to touch lava with a "ten foot pole“, this potentially hazardous activity is all in a day's work for a volcanologist.

• The long pole contains a special probe that can measure the temperature of the lava.

Ring of FireRing of Fire

• major volcanic belt formed by many volcanoes that rim Pacific Ocean

Volcanic belts form along the boundaries of Earth’s plates.

Ring of fire

most volcanoes

occur:

alongdiverging

plateboundaries

along converging

plateboundaries

mid-ocean ridge

in subduction

zones

volcanoes at converging volcanoes at converging boundariesboundaries

subduction causes oceanic crust to sink through a deep-ocean trench into mantle

crust melts & forms magma

magma rises back to surface

forms volcanoes

Volcanoes often form where two oceanic plates collide or where an oceanic plate collides with a continental plate. In both situations, an oceanic plate sinks through a trench. Rock above the

plate melts to form magma, which then erupts to the surface as lava.

island arcisland arc• string of islands created by

volcanoes• examples:

Japan

New Zealand

Caribbean islands

Phillipines

hot spothot spot• area where magma from deep area where magma from deep

within mantle rises & melts within mantle rises & melts thru. crust thru. crust

• can occur:can occur:– in middle of platesin middle of plates– on or near plate boundarieson or near plate boundaries– under continentsunder continents

• eg:eg:– HawaiiHawaii– Yellowstone National ParkYellowstone National Park

Hot Spot Volcanoes• A volcano forms above a hot spot when

magma erupts through the crust and reaches the surface.

The Hawaiian Islands formed one by one over millions of years as the Pacific plate drifted over a hot spot.