* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Fukutoku-Okanoba, Japan
Mono–Inyo Craters wikipedia , lookup
Axial Seamount wikipedia , lookup
Mount Pinatubo wikipedia , lookup
Craters of the Moon National Monument and Preserve wikipedia , lookup
Itcha Range wikipedia , lookup
Mount Garibaldi wikipedia , lookup
Mount Meager massif wikipedia , lookup
Mount St. Helens wikipedia , lookup
Llullaillaco wikipedia , lookup
Mount Pleasant Caldera wikipedia , lookup
Level Mountain wikipedia , lookup
Cerro Blanco (volcano) wikipedia , lookup
Lascar (volcano) wikipedia , lookup
Large igneous province wikipedia , lookup
Potrillo volcanic field wikipedia , lookup
Cascade Volcanoes wikipedia , lookup
Olympus Mons wikipedia , lookup
Volcanology of Io wikipedia , lookup
Mount Edziza volcanic complex wikipedia , lookup
Nevado del Ruiz wikipedia , lookup
Mount Vesuvius wikipedia , lookup
Shield volcano wikipedia , lookup
Mount Pelée wikipedia , lookup
Cerro Azul (Chile volcano) wikipedia , lookup
Wells Gray-Clearwater volcanic field wikipedia , lookup
Earth Science Chapter Six - Volcanoes 6-1 Volcanoes and Plate Tectonics • A volcano is a weak spot in the crust where molten material from the mantle comes to the surface. • A mixture of rock, gases, and water create magma. • Liquid magma that reaches the surface is called lava. When lava cools it forms solid rock. Volcanic activity adds new rock to existing land and forms new islands. 6-1 • Volcanoes occur in belts. One major belt is the Ring of Fire, formed by many volcanoes. Ring of Fire Ring of Fire 6-1 • Volcanic belts form along boundaries where Earth’s plates are diverging (pulling apart) or converging (pushing together). • Most volcanoes occur along diverging plates – the crust is weakened allowing magma to reach Earth’s surface. • Some volcanoes occur in the middle of a plate, far from plate boundaries. At these places, there are HOT SPOTS, magma from deep within the mantle that melts through the crust above it. 6-1 • Over millions of years, a hot spot forms volcano mountains. The Hawaiian Islands were formed as the Pacific plate drifted over a hot spot. – Lava erupted from the hot spot, and built a volcanic island. The Pacific plate kept moving slowly, carrying the island away from the hot spot. This process continued, and over time a chain of islands formed. Hawaiian Islands Formation Hawaiian Islands and their Volcanoes Hualalai Volcano Hualalai Volcano Kilauea volcano is one of the most active on Earth.. Kilauea volcano Mauna Loa Volcano 6-1 – Yellowstone National Park marks a major hot spot under the North American Plate. (Old Faithful – hot water and other materials erupt – this is called a geyser.) Old Faithful Old Faithful Volcano Diagram 6-2 – Volcanic Activity • Lava begins as magma in Earth’s mantle. Magma flows upward through cracks in the rock until it reaches the surface or becomes trapped. As magma rises, the pressure decreases and the dissolved gases begin to separate out. A volcano erupts when an opening develops in weak rock on the surface. During a volcanic eruption, the gases dissolved in magma rush out, carrying magma with them. Magma 6-2 Volcanic Activity • The Volcano – Inside a volcano, magma collects in a pocket called a magma chamber. – The magma moves through the pipe, a long tube that connects the magma chamber to Earth’s surface. – There, the magma leaves the volcano through an opening called a vent. – The area covered by lava as it pours out the vent is called the lava flow. – Lava then collects in a crater, a bowl-shaped area around a volcanoes central vent. Lava Flow 6-2 – Volcanic Activity • The force of an eruption depends on the magma’s gas content: – – – – How the thick or thin the magma is Temperature Silica content Silica is a material formed from oxygen and silicon. Thick magma flows slowly and not so easily. The hotter the magma is, the thinner and faster flowing the magma becomes. Thick magma contains more silica. 6-2 Volcanic Activity • The silica content of magma helps to determine whether the volcanic eruption will be quiet or explosive. – If the magma has low silica, it flows easily and the volcano erupts quietly. Quiet eruptions produce two different types of lava: • Pahoehoe: hot and fast moving lava • aa: cooler, slow moving lava 6-2 Volcanic Activity • A volcano erupts explosively if the magma is thick. The magma plugs the pipe, and pressure builds up until the trapped gases explode, forcing the magma out. A pyroclastic, pyro meaning fire, occurs when an explosive eruptions hurls out ash, cinders, and bombs. 6-2 Volcanic Activity • A volcano that is erupting or has shown signs that it may erupts in the future is called an active volcano. • A volcano that is dormant is not active now, but may again erupt in the future. • An extinct volcano is unlikely to ever erupt again. 6-2 Volcanic Activity • Other forms of volcanic activity: – A hot spring forms when groundwater heated by magma rises to the surface and collects in a pool. – A geyser is a fountain of water and steam that erupts from the ground. – Water heated by magma can provide a clean, reliable energy source called geothermal energy. 6-2 Volcanic Activity • Hazards of volcanoes include: – – – – – Lava flows Clouds of ash Hot volcanic gases Landslides Avalanches of mud, rock, or snow. Lava Flows Clouds of Ash Volcanic Gases Landslides Avalanches 6-3 Volcanic Landforms • Some volcanic landforms are formed when lava flows build up mountains and plateaus. Rock and other materials formed from lava create a variety of landforms including: – Shield Volcano: layers of lava that eventually build up into a sloping mountain. – Cinder Cone: Materials pile up around the vent, forming a steep, cone-shaped hill or mountain. – Composite Volcano: sometimes lava flows alternate with explosive eruptions of ash, cinders, and bombs. The alternating layers form a tall, cone-shaped mountain. – Calderas: a huge hole left by the collapse of volcanic mountain. Shield Volcano Cinder Cone Volcano Composite Volcano Calderas 6-3 Volcanic Landforms • Sometimes magma rises upward through cracks in the crust but does reach Earth’s surface. The magma cools and hardens into rock beneath the surface. Dike A dike forms when magma forces itself across rock layers and hardens. Sill A sill forms when magma squeezes between layers of rock and hardens. Batholiths • Batholiths: forms when a large body of magma cools inside the crust, a mass of rock forms. Active Volcanoes Today • Fukutoku-Okanoba, Japan Merapi, Indonesia Cleveland Volcano, Chuginadak Island, Alaska Colima Volcano - Mexico Karymsky - Russia Popocatepell, Mexico 6-4 Volcanoes in the Solar System • Earth is not the only body in the solar system that shows sign of volcanic activity. – Earth’s moon has dark, smooth areas where lava flowed onto the surface billions of years ago. – Venus has volcanic mountains - shield volcanoes. – Mars has large shield volcanoes similar to those on Venus and Earth. – Jupiter’s moon Io has shown ongoing volcanic eruptions. – Neptune’s moon, Triton, has also shown ongoing volcanic eruptions. Volcanism on the Moon Volcanism on Mars Volcanism on Venus Volcanism on Jupiter - Io