Volcanoes C20-25

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

Magma Melted rock inside Earth Melted rock inside Earth Lava Lava Melted rock that reaches Earth’s surface Melted rock that reaches Earth’s surface

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

Magma Chamber An underground pool that holds hot magma An underground pool that holds hot magma

Crater A large basin formed at the top of a volcano when the top collapses after an eruption A large basin formed at the top of a volcano when the top collapses after an eruption Rain can collect in a crater and form a lake. (Crater Lake, in Oregon) Rain can collect in a crater and form a lake. (Crater Lake, in Oregon)

Ways Volcanoes Form (#1) Plates in the ocean move away from each other. As they move apart, magma rises toward the surface. When it reaches the surface, it hardens to form new ocean floor. Plates in the ocean move away from each other. As they move apart, magma rises toward the surface. When it reaches the surface, it hardens to form new ocean floor.

Ways Volcanoes Form (#2) When ocean and continent plates collide (hit), the ocean plate falls into the mantle and melts. Then it comes to the surface as lava, through a vent. This forms volcanic mountains. When ocean and continent plates collide (hit), the ocean plate falls into the mantle and melts. Then it comes to the surface as lava, through a vent. This forms volcanic mountains.

How Volcanoes Form #3 Plates move over a hot spot in the mantle and hot lava comes through the surface to form volcanic islands. Plates move over a hot spot in the mantle and hot lava comes through the surface to form volcanic islands.

Hawaiian Volcano Hardened Lava

Shield Volcanoes Large, gently sloping mountains Large, gently sloping mountains Form from runny lava Form from runny lava Many are found in Hawaii, rising from the ocean floor Many are found in Hawaii, rising from the ocean floor

Cinder Cone Volcanoes Have steep sides Have steep sides Made of hardened lava chunks Made of hardened lava chunks Not very tall Not very tall

Composite Volcanoes Medium-sized volcanoes Medium-sized volcanoes Made of lava and cinders Made of lava and cinders Have steep peaks and sloping sides Have steep peaks and sloping sides Mt. Fuji (Japan), St. Helens (USA) Mt. Fuji (Japan), St. Helens (USA) Mount Vesuvius in Italy Mount Vesuvius in Italy Explode when they erupt Explode when they erupt

Mt. St. Helens, Washington

Volcanoes Help Earth Minerals deposited into the soil around the volcano help crops grow. Minerals deposited into the soil around the volcano help crops grow. Form new crust on continents Form new crust on continents Form new ocean floor Form new ocean floor

Volcanoes Harm Earth Erupting gasses and hot lava destroy everything in their paths. Erupting gasses and hot lava destroy everything in their paths. Temperature at an eruption point can reach 1470 degrees! The powerful blasts may be felt miles away!

Review Volcanoes form when melted rock called lava flows onto Earth’s surface. Volcanoes form when melted rock called lava flows onto Earth’s surface. Most volcanoes form along plate edges. Most volcanoes form along plate 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 path. They can destroy anything in their path.