Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Physical oceanography wikipedia , lookup
Geomorphology wikipedia , lookup
Geochemistry wikipedia , lookup
Post-glacial rebound wikipedia , lookup
Age of the Earth wikipedia , lookup
History of geology wikipedia , lookup
Oceanic trench wikipedia , lookup
Ring of Fire wikipedia , lookup
Plate tectonics wikipedia , lookup
Chapter 8: Volcanoes The Big Idea: Volcanoes form as a result of tectonic plate motions and occur where magma reaches Earth’s surface. Section 1: Why Volcanoes Form VOCABULARY: 1. Volcano: a vent or fissure in Earth’s surface through which magma and gases are expelled. 2. Magma: liquid rock produced under Earth’s surface, in the crust and mantle. Igneous rocks form from magma. WHY VOLCANOES FORM: Main Ideas: Notes: -Where do volcanoes form? -Mostly on tectonic plate boundaries (plate boundaries that surround the Pacific Ocean have so many volcanoes that the area is called the Ring of Fire). -Volcanoes at -Plates pull apart creating fractures Divergent Boundaries: called fissures. Most volcanoes at Divergent boundaries form under water. Ex: mid ocean ridge (chain of mountains). -Volcanoes at Convergent Boundaries: -Plates collide, the denser plate sinks. As the plate sinks a trench is formed. As the plate subducts into the mantle (subduction), the rock is subjected to heat and pressure, which causes the rock to melt. -Hot Spots: -Volcanically active places not located at tectonic plate boundaries. -Thought to lie directly above columns of hot rock that rise through Earth’s mantle. Ex: Hawaiian Islands. -Hot Spots: as tectonic plates move over a mantle plume, rising magma may cause a chain of volcanoes to form. Hot spot (mantle plume) HOW MAGMA FORMS: Main Ideas: Notes: -Where does magma form? -In the deeper parts of Earth’s crust and the uppermost parts of the mantle, where the temperature and pressure are extremely high. Changes in the temperature and pressure cause magma to form. -Magma forms when temperature of the rock increases and pressure decreases, or when water lowers the melting temperature of a rock.