Ch. 3 Ch. 3 Sec. 1 Volcanoes & Sec. 1 Volcanoes &
Plate TectonicsPlate Tectonics
• weak spot in crust where molten material comes to surface
magmamagma•molten rock from mantle beneath Earth's surface
lava• magma that
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.
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
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
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.