Where the rock cycle begins 8.3 Types of Volcanoes Where the rock cycle begins

Learning Targets Describe the basic shapes of volcanoes Compare the features of volcanoes Describe the stages in the formation of volcanoes

How do volcanoes form? Many layers of lava and ash mix together to make a volcano Different types of volcanoes form from different mixes of ash, gas, and lava

Types of volcanoes What are the 4 main types of volcanoes? Composite/Stratovolcano Shield Cinder cone Supervolcano Determined by type of magma and type of eruption

Composite volcano Stratovolcano Most famous type of volcano Tall mountain with volcanic vent running through the center Viscous lava mixed with pyroclastic material; i.e. composite What does strata- mean? Layer Each eruption = one layer The type of volcano where a large steep mountain is formed from the buildup of layers of lave and volcanic ash is a composite volcano. Lava that has a high viscosity and erupts explosively is most likely to form a composite volcano. Composite materials (also called composition materials or shortened to composites) are materials made from two or more constituent materials with significantly different physical or chemical properties, that when combined, produce a material with characteristics different from the individual components.

Pyroclastic material held together with lava

Composite Volcano Eruption

Shield Volcano Shaped like a shield laid flat Wide, low volcanoes Can be 100 miles wide What type of eruption? Effusive eruptions What type of lava? Low viscosity lava No pyroclastic material The type of volcano that is very wide and flat without steep sides is a shield volcano. Lava that is less viscous, flows easily, and erupts effusively will spread out over a large area to form a shield volcano.

Shield Volcano Formation

Cinder Cones Smallest and most common Usually only erupt once Sometimes form around other volcanoes Formed by lava or pyroclastic material? Only pyroclastic material; no lava The most common and smallest type of volcano is a cinder cone. Eruptions that rarely produce flowing lava and form small steep volcanoes made rimarily from pyroclastic material are characteristic of cinder cone volcanoes. A cinder is a pyroclastic material. Cinders are extrusive igneous rocks. Cinders are similar to pumice, which has so many cavities and is such low-density that it can float on water. Cinder is typically brown, black, or red depending on its chemical content

Cinder Cone Formation

Supervolcanoes Huge volcanic features Eruptions so powerful only a caldera remains A caldera is a Volcanic Crater Eruptions are rare, but can change global climate and life on earth A lot is unknown due to rarity of eruptions What volcano result in the largest and most explosive eruption? Supervolcano Yellowstone is thought to be an example of the most dangerous type of volcano in which a single eruption could potentially change all life on the planet. supervolcano

Caldera of a Supervolcano

Mt. Pinatubo Eruption; not a supervolcano

Last Yellowstone supervolcano supereruption: 640,000 years ago Yellowstone Magma Chamber Mt. Pinatubo Magma Chamber

Types of volcanoes and causes Composite Subduction zones Shield Hot spots Cinder cone Variable Supervolcano Enormous hot spots under continents

Where the rock cycle begins 8.4 Volcanic Landforms Where the rock cycle begins

Learning Targets List and describe landforms created by lava Explain how magma creates different landforms Describe the processes that create hot springs and geysers.

Volcanic features Lava can form Lava domes: reforming volcanoes Lava plateaus: lava erupted on flat ground Volcanic islands: Island arc or hot spot chain What type of rock is this? Extrusive Igneous Magma can form Intrusive igneous rocks Small pebbles to huge batholiths A batholith (from Greek bathos, depth + lithos, rock) is a large emplacement of igneous intrusive (also called plutonic) rock that forms from cooled magma deep in the Earth's crust.

Growing Lava Dome

Crater Lake; Caldera with Lava Dome

Cascades Lava Plateau

Lava Plateau: Like a flood that becomes solid rock

Remains of ancient magma (intrusive) A batholith (from Greek bathos, depth + lithos, rock) is a large emplacement of igneous intrusive (also called plutonic) rock that forms from cooled magma deep in the Earth's crust.

Hot springs and Geysers Water reacts with nearby magma to form Hot springs: hot water under normal pressure Geysers: hot water that erupts under high pressure Why might people think this water has medicinal properties? Hot water holds a lot of minerals Water that is heated underground and erupts violently as a result of the build up of pressure creates a geyser.

Edge of Pyroclastic Flow