Survey
* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Download Volcanism - MsMonroesScience
Document related concepts
Transcript
Volcanism Ch. 18 Volcanoes Volcanoes ___________________________________________________________ Magma is a slushy mixture of _______________________________________________. Once magma forms, _______________________________________________________ _____________________________________ and crust. Magma that _________________________________________________________ Volcanism describes all the processes associated with the _______________________________ _____________________________ The distribution of volcanoes on Earth’s surface is _______________________________ Most volcanoes ______________________________________________________ The majority ____________________________________________________________. Along these margins, _____________________________________________________ ___________________________________________ erupts far from plate boundaries. Tectonic plates collide at convergent boundaries, which can form subduction zones – _________ _______________________________________________________________________ _________________________________________________________, magma forms. ____________________________________________ because it is less dense than the surrounding solid material. As it rises, the ___________________________________________________________ from the overlying plate. Most volcanoes located on land result from ____________________________________ These volcanoes are ______________________________________________________. The volcanoes associated with _____________________________________________________ The Circum-Pacific Belt is also called the ______________________________________ The outline of the belt ______________________________________________. ________________________________________________________________________ It includes _____________________________________, two volcanoes in Italy. Its general outlines correspond to the _________________________________ ________________________________________ At divergent plate boundaries tectonic plates move apart and ____________________________ ___________________________________________________________ At ocean ridges, _______________________________________________________ and is called pillow lava. Unlike the explosive volcanoes that occur at convergent plates, ___________________ ____________________________________________________________, with effusions of large amounts of lava. Some volcanoes form ______________________________________________________. Scientists hypothesize that hot spots are ___________________________________ ________________________________________________________rise to the surface. Some of Earth’s __________________________________________________________ under the ocean. The Hawaiian islands are ____________________________________________. As the __________________________________________, it formed volcanoes. The hot spot formed by the magma plume ___________________________________________ ___________________________________________ Over time, the hotspot ____________________________________________________ ______________________________. The volcanoes on the oldest Hawaiian island, Kauai, are _________________________ _____________________________________________________________ ______________________________________________________________________, on the Big Island of Hawaii, is currently located over the hot spot. Chains of volcanoes that form over stationary hot spots _________________________________ ________________________________________ _____________________________________________________________________ from the positions of these volcanoes. Flood Basalts ______________________________________________________________________________, they can lead to the formation of flood basalts. Flood basalts form when ___________________________________________________ ________________________________________________________________________ Over hundreds or even thousands of years, ____________________________________ _________________________________________ Anatomy of a Volcano ______________________________________________________________________________ _______________________________________, and emerges through an opening called a vent. As lava flows through the vent and out onto the surface, _________________________ __________________________ _______________________________________________________________________ _______________________________ known as a volcano. At the top of a volcano, around the vent, ______________________________________. Volcanic craters are ______________________________________________________________ _______________________________________________________________, can be up to 50km in diameter. Calderas often form after the _______________________________________________ ________________________________________ _______________________________________________________________________ ___________________________________, leaving an expansive, circular depression. Types of Volcanoes The appearance of a volcano depends on two factors: __________________________________ ____________________________________________________________________ Based on these two criteria, ________________________________________________. _______________________________________________________________________. A ____________________________________ is a mountain with broad, gently sloping sides and a _________________________________________________. Shield volcanoes form when layers of lava _____________________________________. They are the ____________________________________________. Mauna Loa When eruptions eject small pieces of magma into the air, ____________________________ form as this material, called tephra, _______________________________________________. Cinder cones ___________________________________________________________ Cinder cones _____________________________________________________________ Lassen Volcanic Park cinder cone. _______________________________________ are formed of layers of hardened chunks of lava from violent eruptions ___________________________________________________________ __________________. ______________________________________________________________________ _____________________________, and are much larger than cinder cones. Because of their explosive nature, ___________________________________________ ___________________________________________ Mount Augustine What makes the eruption of one volcano quiet, and the eruption of another explosively violent? ________________________________________________________________________ Lava from an eruption can be _______________________________________________. In order to understand why volcanic eruptions are not all the same, ________________ _______________________________________________________________________ Temperature – ___________________________________________, most rocks begin to melt at temperatures between 800 and 1200 degrees Celsius. Such temperatures are ____________________________________________________. In addition to temperature, _________________________________________________ _______________________________________ Pressure – _____________________________________________________________________ _______________________________. As pressure increases, _____________________________________________________. The effect of pressure explains why _________________________________________ ____________________________________________________ Composition of Magma The composition of magma determines a volcano’s explosivity, __________________________ ____________________________________________ Scientists now know that the factors that affect the composition of magma include the ______________________________________________________________________ _______________________________________________________, and – very significantly – the amount of silica a magma contains. Understanding the factors that determine the behavior of magma can _____________________ _____________________________________________________ Dissolved Gases In general, __________________________________________________________________, the magma’s explosivity also increases. In the same way that gas dissolved in soda gives the soda its fizz, ___________________ _________________________________________________________________ ________________________________________________ dissolved gas in magma. The presence of water vapor _________________________________________. The presence of dissolved water vapor lowers the melting temperature of minerals, _________________________________________________________ Viscosity The physical property that _______________________________________________________ ________________________________ _______________________________________________________________________. In general, ____________________________________________________________ so it tends to resist flowing. Magma with _____________________________________________________________. Because it is thick, magma with high silica content _______________________ _________________________________________________ In general, magma with low silica content has low viscosity – it tends to be thin and runny. So it ______________________________________________________________. Types of Magma The silica content of magma determines not only its explosivity and viscosity, _____________ _______________________________________________________________ _______________________________________________________________, basaltic magma typically forms. It typically has the same silica content as the rock basalt – _______________________________________________ Its low silica content produces low-viscosity magma. ___________________ ______________________________________________________ The resulting volcano is ___________________________________________. ________________________________ has the same silica content as the rock andesite – _____________________________________ The source material for this magma can be _____________________________________ Because of its higher silica content this magma has an intermediate viscosity. Thus the volcanoes it ____________________________________________________________. ______________________________________________________________________________ ___________________________ rich in silica and water, it forms rhyolitic magma. Rhyolitic magma has the same composition as the rock granite – __________________. ________________________________________________________________________ ____________________, makes the volcanoes fueled by rhyolitic magma very explosive. Explosive Eruptions When lava is too viscous to flow freely from the vent, __________________________________ until the volcano explodes, ___________________________________________________. ____________________________________________________________________. Tephra can be pieces of lava that solidified during the eruption, or _________________ __________________________________________________________________ Tephra are _____________________________________. ____________________________________________________________________. _______________________________________________________________________. Some blocks can be the size of a car. Large explosive eruptions can ____________________________________________________. Ash can pose a ___________________________________________________________ Pyroclastic Flows Some tephra cause ______________________________________________________________ ________________________________________________________________________ ___________________________________ at speeds of 80 km/h. Rapidly moving _________________________________________________________ ____________________________ are called pyroclastic flows. They can have ____________________________________________________________ Intrusive Activity _____________________________________________________________________________ because not all magma emerges at the surface. Before it gets to the surface, ________________________________________________. Magma can ______________________________________________and enter the newly formed fissures. Magma can also cause blocks of rock to break off and sink into the magma, ____________________________________________________ Finally magma can ________________________________________________________. What happens deep in Earth ____________________________________________? Over a long period of time, _________________________________________________ ___________________________________________ _______________________________________________________________ only a few centimeters thick and several hundred meters long. ________________________________________ These intrusive igneous rock bodies, ___________________________ can be exposed at Earth’s surface as a result of uplift and erosion and are classfied ______________________________________________________________. Batholiths and Stocks _________________________________________________________________________. ________________________________________________________________________ ________________ that cover at least 100 square km and take millions of years to form. Batholiths are ____________________________________________________________ Many batholiths in North America are composed primarily of granite – ______________ ___________________________________________________ The largest batholith in North America is the ___________________________________ ________________________________________________________________________ but smaller in size are called stocks. _____________________________________________________________________ and generally form 5 to 30 km beneath Earth’s surface. Laccoliths Sometimes when magma intrudes into parallel rock layers close to Earth’s surface, ___________ _____________________________________________________________ of the magma body. A laccolith is a ___________________________________________________________. Compared to batholiths and stocks, __________________________________________. Laccoliths exist in the _____________________________________, and the Judith Mountains of Montana. Sills ______________________________________________________________________________ A sill can range from only a _________________________________________________ _______________________________________________________________________ Because it takes great amounts of force to lift entire layers of rock, ________________ _______________________________________________ Another effect of sills is to __________________________________________________ Unlike a sill, which is parallel to the rocks it intrudes, ___________________________________ ____________________________________ Dikes often form when ____________________________________________________ A volcanic neck occurs _____________________________________________________ Dikes are often ____________________________________________________
