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Chapter 9 Volcano!
| Question | Answer |
|---|---|
| Magma | Molten rock under the Earth's surface |
| Lava | Once magma reaches the Earth's surface, it is called lava |
| Volcanoes | Areas of Earth's surface through which magma and volcanic gases pass. |
| Explosive erruptions | hot debris, ash, and gas rapidly shoot out. (pyroclastic materials) Can be very destructive |
| Non explosive erruptions | Most common type of eruption. Can release huge amounts of calm lava flows. |
| Magma Chamber | Part of the volcano- it is a body of molten rock deep underground that feeds the volcano. |
| Throat | Part of the volcano- cracks in in Earth's surface that connect the magma chamber to the vent; allows the magma to travel up to the surface. |
| Vent | Part of the volcano- openings in the Earth's crust that allow magma and pyroclastic material to erupt from the volcano. |
| Composition of Magma | The composition of magma can determine how explosive a volcano can erupt. 3 things in magma that can make it more explosive: water, silica, and gas. |
| How does water in magma create a more explosive erruption? | Water is dissolved in the magma deep underground. Then when it moves up toward the surface, the pressure decreases. This allows the gas to expand, thus creating more pressure. More pressure = more explosive. |
| How does silica in magma create a more explosive erruption? | Silica= silicon and oxygen, a common mineral in rocks. Magma w/ lots of silica has a high viscosity, meaning the liquid moves slowly. The magma can cool in the vent and clog the volcano, building pressure from magma pushing up and gases not able to escape |
| Pyroclastic material | Is formed when the magma is blasted into the air and hardens. Is the main product of an explosive eruption |
| Types of Lava | Aa, pahoehoe, blocky and pillow |
| Aa Lava | Forms sharp, brittle crust. Has low viscosity, moves quickly. Do not want to step on this! Ouch! |
| Pahoehoe Lava | (pah-hoy-hoy) Has a high viscosity, flows slow. Forms smooth, glassy surface with wrinkles. |
| Pillow Lava | Forms on ocean floor from underwater volcanoes. Has a high viscosity, creates pillow shaped lava. Outer lava cools, then cracks like an egg, pushing hot magma to surface, cooling it and repeating the process until it is completely cooled |
| Blocky Lava | Has a cool, stiff consistency - high viscosity. Does not travel far from the volcano. Forms jumbled heaps of shap-edged, block shaped lava chunks. |
| Volcanic Bomb | Type of pyroclastic material. Large blob of magma that has cooled in the air. Blob shaped from lava spinning through the air as it cooled. |
| Lapilli | Type of pyroclastic material. "Little stones" in Italian. Pebble like bits of magma that hardened before hitting the ground |
| Volcanic Block | The largest type of pyroclastic material. Piece of solid rock that erupted from a volcano- from volcano/mountain side. |
| Volcanic Ash | Type of pyroclastic material. Forms when gases in stiff magma expand rapidly and the walls of the gas bubbles explode into tiny, glass like slivers. Most common type of pyroclastic material. |
| Pyroclastic Flow | Enormous amounts of hot ash, dust and gases that are ejected from a volcano. They can race down a mountian side 200-700 km/hr. The center can reach over 700 degrees celcius. |
| Climate Change | An effect from a large volcanic erruption. Occurs when ash and gases are ejected high into the atmosphere. Ash can block out the sun. World wide temp. decrease. Crop failure. Starvation/death/crop price increase |
| Types of volcanoes | 1. shield 2. cinder cone 3. composite |
| Shield volcano | Created from repeated non explosive erruptions. Lava spreads out over wide areas. Have gently sloping sides. Entirely made of lava. Largest volcano in solar system is this type- on mars |
| Cinder cone volcano | Created from moderately explosive eruptions. Made entirely of pyroclastic material. Can form in clusters on the sides of other volcanoes. Erode quickly. |
| Composite Volcano | Created from explosive erruptions. Made of pyroclastic material that is followed by calm flows of lava. Also called a stratovolcano. The layering makes the structure strong, so it will last a long time. They are the most common type of volcanoes. |
| Crater | Form at the top of the central vent of many volcanoes. Funnel shaped pit. Created by less explosive erruptions- lava and pyro. build up. lava drains back underground. vent can collapse to make a large crater. |
| Caldera | Much larger than craters. Semicircular depression that forms when the magma chamber partially empties and chamber roof collapses. The ground above chamber collapses. |
| Lava Plateaus | Wide, flat landrom that results from non explosive eruptions. Lava erupted from long cracks (rifts) over millions of years. Lava has low viscosity, so can spread over a large area and build up over time. |
| How does magma form? | Rock melts when its temperature increase or pressure decreases. Magma forms at plate boundaries (less pressure). Once magma is formed, it is less dense than surrounding rock, so it moves up to the surface. |
| Where do volcanoes form? | plate boundries or hot spots |
| Divergent Boundary | tetonic plates move away from each other. As tectonic plates separate, a rift zone is created. 15% of volcanoes on land are formed this way. |
| Rift zone | A set of deep cracks that form between divergent plates. |
| How does magma form and move between divergent boundaries? | When the rift zone is created, the pressure decreases and the rocks melt. The melted rock is less dense than the surroundng rock, so it rises above the surrounding rock. |
| Mid-ocean ridges | Volcanoes and mountain chains undersea that are produced by lava flowing from undersea rift zones. |
| Convergent boundry | A place where tectonic plates collide. |
| How does magma form and move between convergent boundaries? | As the oceanic crust moves downward, it becomes hotter and releases water. The water lowers the melting point of rock in the mantle and helps magma form. Magma is less dense than surrounding rock, so it will rise to surface. |
| Subduction | The movement of one tectonic plate underneath another. Oceanic plates moves underneath continental plates. |
| Hot spot | vocanically active places on the Earth's surface that are far from plate boundries. There are 2 theories about why they form. |
| Mantle plumes | Columns of rising magma deep underground that create hot spots |
| What can hot spots produce? | Chains of volcalanoes, such as the Hawaiian islands. |
| What are the three classifications for volcanoes? | Active, Dormant, Extinct. |
| Active Volcano | Are currently erupting or show signs of erupting in the near future |
| Dormant Volcano | Are currently not erupting, but the record of past eruptions suggest they can erupt again. |
| Extinct Volcano | They have not erupted in recorded history and probably never erupt again |
| Signs that an eruption will take place | 1. Earthquakes are frequent and increasing intensity. 2. Slope of volcano is changing. Magma is pushing on the inside of the sides of the volcano, making it change its shape. 3. Ifrared is used to see if the temperature of the volcano is increasing. |
| Ring of Fire | A "circle" of active volcanoes that occur around the Pacific ocean, occuring along plate boundries. |
Created by:
kibbylj
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