VolcanoesVolcanoes

C20-25C20-25

VolcanoVolcano

A mountain formed A mountain formed when red-hot melted when red-hot melted rock flows through a rock flows through a crack onto the earth’s crack onto the earth’s surfacesurface

MagmaMagmaMelted rock inside EarthMelted rock inside Earth

LavaLavaMelted rock that reaches Melted rock that reaches Earth’s surfaceEarth’s surface

VentVentA rocky opening that A rocky opening that magma flows through magma flows through to reach the surface to reach the surface of Earthof Earth

Magma ChamberMagma ChamberAn underground pool An underground pool that holds hot magmathat holds hot magma

CraterCraterA large basin formed at A large basin formed at the top of a volcano when the top of a volcano when the top collapses after an the top collapses after an eruptioneruption

Rain can collect in a crater Rain can collect in a crater and form a lake. (Crater and form a lake. (Crater Lake, in Oregon)Lake, in Oregon)

Ways Volcanoes Form Ways Volcanoes Form (#1)(#1)

Plates in the ocean move Plates in the ocean move away from each other. As away from each other. As they move apart, magma rises they move apart, magma rises toward the surface. When it toward the surface. When it reaches the surface, it reaches the surface, it hardens to form new ocean hardens to form new ocean floor.floor.

Ways Volcanoes Ways Volcanoes Form (#2)Form (#2)

When ocean and continent When ocean and continent plates collide (hit), the ocean plates collide (hit), the ocean plate falls into the mantle and plate falls into the mantle and melts. Then it comes to the melts. Then it comes to the surface as lava, through a vent. surface as lava, through a vent. This forms volcanic mountains. This forms volcanic mountains.

How Volcanoes FormHow Volcanoes Form#3#3

Plates move over a hot Plates move over a hot spot in the mantle and spot in the mantle and hot lava comes through hot lava comes through the surface to form the surface to form volcanic islands.volcanic islands.

Hawaiian Volcano Hawaiian Volcano

Hardened Lava

Shield VolcanoesShield VolcanoesLarge, gently sloping Large, gently sloping mountainsmountains

Form from runny lavaForm from runny lavaMany are found in Many are found in Hawaii, rising from the Hawaii, rising from the ocean floorocean floor

Cinder Cone VolcanoesCinder Cone Volcanoes

Have steep sidesHave steep sidesMade of hardened Made of hardened lava chunkslava chunks

Not very tallNot very tall

Composite Composite VolcanoesVolcanoes Medium-sized volcanoesMedium-sized volcanoes

Made of lava and cindersMade of lava and cinders Have steep peaks and sloping Have steep peaks and sloping

sidessides Mt. Fuji (Japan), St. Helens (USA)Mt. Fuji (Japan), St. Helens (USA) Mount Vesuvius in ItalyMount Vesuvius in Italy Explode when they eruptExplode when they erupt

Mt. St. Helens, WashingtonMt. St. Helens, Washington

Volcanoes Help EarthVolcanoes Help EarthMinerals deposited into the Minerals deposited into the soil around the volcano help soil around the volcano help crops grow.crops grow.

Form new crust on continentsForm new crust on continentsForm new ocean floorForm new ocean floor

Volcanoes Harm EarthVolcanoes Harm Earth Erupting gasses and hot lava Erupting gasses and hot lava destroy everything in their destroy everything in their paths.paths.

Temperature at an eruption Temperature at an eruption point can reach 1470 degrees!point can reach 1470 degrees!

The powerful blasts may be felt The powerful blasts may be felt 10-15 miles away! 10-15 miles away!

ReviewReview Volcanoes form when melted rock Volcanoes form when melted rock

called lava flows onto Earth’s surface.called lava flows onto Earth’s surface. Most volcanoes form along plate Most volcanoes form along plate

edges.edges. They add crust and ocean floor.They add crust and ocean floor. They add minerals to the soil.They add minerals to the soil. They can destroy anything in their They can destroy anything in their

path.path.