Question | Answer |
Volcano | A weak spot in the crust where molten material, or magma, comes to the surface |
Magma | a molten mixture of rock forming subtances, gases, and water from the mantle |
Lava | Liquid magma that reaches the surface; also the rock formed when liquid lava hardens |
Ring of Fire | A major belt of volcanoes that rims the Pacific Ocean |
Island arc | A string of islands formed by the volcanoes along a deep- ocean trench |
Hot spot | An area where material from deep within the mantle rises and then melts, forming magma |
Where do volcanic belts form? | Along the boundaries of Earth's plate |
Where do volcanoes form and when? | Above a hot spot when magma erupts through the crust and reaches the surface |
Element | A substance that cannot be broken down into other substances |
Viscosity | The resistance of a liquid to flowing |
Compound | A substance made of two or more elements that have been chemically combined |
Silica | The compound that is made up of particles of the elements oxygen and silicon |
Physical property | Any characteristic of a substance that can be observed or measured without changing the composition of the substance |
Chemical property | Any property that produces a change in the composition of matter |
Pahoehoe | Fast- moving hot lava that has low viscosity |
Aa | Lava that is cooler and slower moving |
Why do some liquids flow more easily than others? | Liquids differ in viscosity |
What does the viscosity of magma depend on? | Its silica content and temperature |
What has a particular set of physical and chemical properties? | Substances. These properties can be used to identify a substance or to predict how it will behave |
Physical or Chemical?
Density | Physical |
Physical or Chemical?
Boiling Point | Chemical |
Physical or Chemical?
Ability to burn | Chemical |
Physical or Chemical?
Ability to react with other substances | Chemical |
Physical or Chemical?
Hardness | Physical |
Physical or Chemical?
Magnetic quality | Chemical |
Magma chamber | The pocket beneath a volcano where magma collects |
Pipe | A long tube through which magma moves from the magma chamber to Earth's surface |
Vent | The opening through which molten rock and gas leave a volcano |
Lava flow | The area covered by lava as it pours out of a vent |
Crater | A bowl shaped area that may form at the top of a volcano around the central vent |
Pyroclastic flow | The expulsion of ash, cinders, bombs, and gases during an explosive volcanic eruption |
Dormant | Describes a volcano that is not currently active, but that may become active in the future |
Extinct | Describes a volcano that is no longer active and is unlikely to erupt again |
What happens when a volcano erupts? | The force of the expanding gases pushes magma from the magma chamber through the pipe until it flows or explodes out of the vent |
How do geologists classify volcanic eruptions? | Quiet or explosive |
What terms do geologists use to describe a volcano's stage of activity? | Active, dormant, or extinct |
Why does magma in the mantle rise through the crust above it? | The crust is less dense, the pressure from the gasses in the magma chamber, comes up from the weakest spot on the crust |
As magma rises toward the surface, what happens to the gases in it? Why? | The dissolved gases begin to expand, forming bubbles and exploding |
Contrast the viscosity of magma in quiet and explosive eruptions | Quiet eruptions: Low viscosity, low silica, high temp
Explosive eruption: High viscosity, high silica, low temp |
How does an explosive eruption produce a pyroclastic flow? | Breaks lava into fragments that cool and harden into pieces of different sizes. Mixture of ash, cinders, and bombs |
Describe the stages of volcanic activity | Active, dormant, extinct |
Shield volcano | A wide, gently sloping mountain made of layers of lava and formed by quiet eruptions |
Cinder cone volcano | A steep, cone- shaped hill or small mountain made of volcanic ash, cinders, and bombs piled up around a volcano's opening |
Caldera | The large hole at the top of a volcano formed when the roof of a volcano's magma chamber collapses |
Composite volcano | A tall cone-shaped mountain in which layers of lava alternate with layers of ash and other volcanic materials |
Volcanic neck | A deposit of hardened magma in a volcano's pipe |
Batholiths | A mass of rock formed when a large body of magma cools inside the crust |
Dike | A slab of volcanic rock formed when magma forces itself across rock layers |
Sill | A slab of volcanic rock formed when magma squeezes between layers of rock |
Geothermal activity | The heating of underground water by magma |
Geyser | A fountain of water an steam that builds up pressure underground and erupts at regular intervals |
What do volcanic eruptions create? | Land forms made of lava, ash, and other materials. These land forms include shield, cinder cone, composite volcanoes, and lava plateaus |
What features are formed by magma? | Volcano necks, dikes, sills, batholiths and dome mountains |
What are two types of geothermal activity and where are they found? | Hot springs and geysers are often found in areas of present or past volcanic activity |
Name each type of volcano and how is each formed? | Shield: Quiet eruption, lava flows build up a sloping mt.
Cinder Cone: Explosive eruption, ash, cinders, and bombs build up around the vent in a hill
Composite: Quiet & Explosive eruption, lava flow then ash, cinders, and bombs (alternating) |
How does a lava plateau form? | When floods of lava flow with low viscosity are on top of earlier floods |
What happens to create a caldera? | An eruption has to empty the main vent and the magma chamber and the mountain collapses inward |
Why is volcano soil so fertile? | It contains nitrogen, potassium, and phosphorus |
What are two uses of geothermal energy? | Heating homes and electricity |