VOLCANOES

VOCABULARY Minerals – An inorganic solid with a specific chemical composition Magma – Liquid or molten rock under ground Lava – Magma that has reached the Earth’s surface

VOCABULARY Vent – The main outlet for magma to escape Crater – A large, funnel-shaped pit created by an eruption Magma Chamber– A large underground pool of molten rock found beneath the surface of the Earth.

THE FORMATION OF MAGMA Magma can be formed under three conditions: Temperature – the melting point of the minerals is reached. Pressure – can decrease the melting point Fluids can decrease the melting point of minerals

VOLCANO A volcano is a vent in Earth’s surface where magma and gases are expelled.

VOLCANISM Volcanism - Any activity that includes the movement of magma onto Earth’s surface Magma rises upward because it is less dense than the surrounding rock. The amount of magma increases as it reaches the surface: It melts some of the surrounding rock on its way up Large chunks of rock break off and melt.

This zone of active volcanoes is formed by the subduction of plates along the Pacific coasts and neighboring plates. As the oceanic plate sinks below another, water combines with crust and mantle material. The water lowers the melting point of the rock and magma is formed. THE RING OF FIRE

RING OF FIRE

HOW DO I FIND A VOLCANO? Subduction zones are just one area of major volcanic action. They are where one plate slides under another. Mid-ocean ridges: The best place to find large amounts of magma are where two plates move apart. Hot Spots Areas of volcanism in the middle of a plate

3 TYPES OF ERUPTIONS LAVA FLOW eruption A mass of flowing or solidified lava. One of three formations maybe be created: Pahoehoe Aa Blocky lava

3 TYPES OF ERUPTIONS Quiet eruptions Quiet eruptions are characterized by: Continuous flow of lava over large areas Leakage of gases The lava does not harden and block the vent, allowing for flow and less violent explosions

QUIET ERUPTIONS

3 TYPES OF ERUPTIONS Explosive eruptions are due to sluggish lava. The lava cools quickly to form plugs in the vent. When the volcano erupts, it does so violently due to the back up of pressure. These types tend to throw clouds of gas, ash and other solid particles (pyroclastic material)

EXPLOSIVE ERUPTIONS

TYPES OF VOLCANOES

SHIELD VOLCANOES Features: Broad base and sloping sides Covers a wide area Generally form from quiet eruptions of constantly flowing lava Example: Hawaiian Islands

CINDER CONE VOLCANO Features Very steep slopes, but smaller than the other two Form from small explosive eruptions Commonly have craters due to the explosive erupting. Example: Capulin Volcano in NM

COMPOSITE VOLCANOES Features Made from alternating layers of hardened lava flows and volcanic ash/dust (pyroclastic material) Formed by both quiet and explosive eruptions Create large volcanic mountains Example: Mt. Fuji in Japan

The upward movement of magma in a vent can cause the surface of a volcano to bulge outward. Some volcanoes can be tracked to establish any activity patterns, similar to Old Faithful. Pressure can grow inside the rock surrounding the magma. This may cause small earthquakes Temperature changes inside the rock can cause fracturing and small earthquakes An increase in strength and frequency of earthquakes may be a predictor of an upcoming eruption PREDICTING AN ERUPTION INCREASE IN EARTHQUAKE ACTIVITYPATTERNS IN ACTIVITY

POP QUIZ! NAME THESE THREE TYPES OF VOLCANOES