Volcanoes How they help change the surface of the earth. Dr. Cyndi Orsburn

What is a Volcano? A volcano is a mountain with one or more fissures or cracks where liquid rock, or magma, can travel upward from deep within the earth. Once it reaches the surface, the magma is called lava. The Earth's internal heat melts the magma and causes gases inside the mountain to expand. When the pressure from these expanding gases builds, an eruption may occur. Liquid rock pushes through the mountain's cracks and flows upward, along with gas and other material.

What Erupts Out of a Volcano? A pyroclastic flow is a mixture of hot gas and bits of rock, ash, pumice and glass. It moves very quickly, destroying trees, homes and anything in its path. If the pyroclastic flow becomes saturated with water, it can change into a lahar--a mudflow. An ash cloud may rise 12 miles into the air in as little as 30 minutes following a volcanic eruption. This cloud spreads over a wide area, and particles may be dangerous if inhaled The lava flow also damages the landscape, changing it for centuries to come. Volcanic bombs are lava fragments that were ejected while viscous (partially molten) and larger than 64 mm in diameter.

How do volcanoes change the Earth? The ground you walk upon was probably deposited by a volcano. Over 80 percent of the Earth is covered by volcanic rock. Volcanoes also formed the atmosphere we breathe. The name volcano has its origin from the name of Vulcan, a god of fire in Roman mythology.

What are the layers the Earth is made of? Crust The crust is the outer layer of Earth. It is about 18 miles thick. It is the part we live on. Mantle The second layer is called the mantle. It is about 1,800 miles thick. Core The inner layer is called the core. The Earth's core consists of a fluid outer core and a solid inner core. Because the outer core contains iron, when it flows it generates a magnetic field. This is the source of the Earth's magnetic field.

Plate Tectonics The intense heat of the liquid magma core simmering beneath the crust causes the Earth’s surface to slowly reshape itself. Plate tectonics refers to how the Earth’s surface is built of plates. Earth’s rocky plates are growing and spreading apart causing earthquakes, fueling volcanic eruptions, and raising mountains. Each year these eruptions spread more than three times as much molten rock under the ocean, than do all the volcanoes on land.

Earth’s Major Plates The current continental and oceanic plates include: the Eurasian plate, Australian-Indian plate, Philippine plate, Pacific plate, Juan de Fuca plate, Nazca plate, Cocos plate, North American plate, Caribbean plate, South American plate, African plate, Arabian plate, the Antarctic plate, and the Scotia plate

Ring of Fire The Ring of Fire is a zone of frequent earthquakes and volcanic eruptions that encircles the basin of the Pacific Ocean. It is shaped like a horseshoe and it is 40,000 km long. It is associated with a nearly continuous series of oceanic trenches, island arcs, and volcanic mountain ranges and/or plate movements. 90% of the world's earthquakes and 81% of the world's largest earthquakes occur along the Ring of Fire. The Ring of Fire is a direct consequence of plate tectonics and the movement and collisions of crustal plates

What causes volcanoes to erupt? . The Earth's crust is made up of huge rocky slabs called plates, which fit together like a jigsaw puzzle. These plates sometimes move. Between the Earth's crust and the mantle is a substance called magma which is made of rock and gases. When two plates collide, one section slides on top of the other, the one beneath is pushed down.  Magma is squeezed up between two plates

Volcano Types – 1. Composite Volcano The classic volcano is called a stratovolcano or composite volcano because it consists of layers of solid lava flows mixed with layers of sand- or gravel-like volcanic rock called cinders or volcanic ash. These volcanoes form from layers of melted rock. They are steep-sided, and cone shaped. Some of the most beautiful mountains in the world are composite volcanoes. This type of volcano usually erupts in a very explosive way, from the viscous magma. The viscous magma gets stuck in the pipes and is trapped. This causes the pressure to increase, which causes an explosive eruption. The composite cone is the most deadly type of volcano. These volcanoes are typically tens of miles across and ten thousand or more feet in height. Examples are: Mt. Vesuvius, Krakatoa, Fujiyama, and Mount St. Helens. Mayon Volcano

Volcano Types – 2. Cinder Cone Volcano The "cinder cone“ volcano or scoria cones consist almost entirely of loose, grainy cinders and almost no lava. The most common type of volcano, Cinder cones are the smallest type of volcano. They are circular or oval shaped and their crater is bowl shaped. These volcanoes grow very fast until they reach their maximum height. Cinder cone volcanoes form from small, jagged pieces of rock and ash, also known as cinders, thrown in the air during an explosion. Examples are Mauna Kea, Sunset Crater and La Paruna. Cinder cones look like fat, upside-down ice cream cones with a vent, or opening, at the top. Mount Kilauea

Volcano Types - 3. Shield Volcanoes Hawaii has many shield volcanoes with low slopes that consist almost entirely of frozen lavas. They are built mainly from lava flows. After an eruption the lava flows out of the vents and creates sloping sides. Their shape is similar to a warrior’s shield. When a shield volcano erupts it is not usually explosive. Sometimes instead of lava flowing from the vents of a shield cone, the lava pours out of long fissures, which is why they are so wide. They almost always have large craters at their summits. Shield volcanoes are short, bowl-like hills with gradually sloping sides. Mauna Loa, a shield volcano on the "big" island of Hawaii, is the largest single mountain in the world, rising over 30,000 feet above the ocean floor and reaching almost 100 miles across at its base. Mauna Loa

Volcanic Features A caldera is a volcanic feature formed by the collapse of land following a volcanic eruption. They are often confused with volcanic craters. The word 'caldera' comes from the Spanish language, meaning "cauldron". A volcanic fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is usually a few meters wide and may be many kilometers long. Fissure vents can cause large flood basalts and lava channels. This type of volcano is usually hard to recognize from the ground and from space because it has no central caldera and the surface is mostly flat. The volcano can usually be seen as a crack in the ground or on the ocean floor. Narrow fissures can be filled in with lava that hardens.

Main Parts of a Volcano 1. Magma chamber – where magma is stored unfer the volcano 2. Bedrock - solid rock present beneath the ground 3. Conduit – pipe that magma flows out of to surface 4. Base – lowest part or bottom of a volcano 5. Sill - A flat piece of rock formed when magma hardens in a crack in a volcano 6. Branch pipe – side conduit of volcano 7. Layers of ash emitted by the volcano 8. Flank – side of volcano 9. Layers of lava emitted by the volcano 10. Throat – entrance of a volcano 11. Parasitic cone – small cone formed by volcanic debris 12. Lava flow - where lava flows out 13. Vent – opening where lava can flow 14. Crater – bowl shaped where vent is 15. Ash cloud – cloud formed from ash

Different Types of Lava Flows Pāhoehoe lava has a smooth, billowy, undulating, or ropy surface. Pahoehoe flow is very viscous, that means that it is thin and liquid. It has a smooth surface that dries pretty quickly and becomes thicker and flows more slowly than the still hot lava below the surface. ‘Aʻā lava is characterized by a rough or rubbly surface composed of broken lava blocks called clinker. It looks like little lava spines are sticking up from the lava as it moves. The lava is like paste because it is so thick and the clinkers travel on top of the lava flow A lava flow is a molten river of melted rock. Lava flows do not come from explosive eruptions, but they just pour out of the top of a vent slowly. Lava flows burn and destroy everything in their paths. Pillow lava is formed when lava emerges from an underwater volcanic vent or a lava flow enters the ocean. The viscous lava forms a solid crust immediately upon contact with the water. Then, this crust cracks and oozes additional large blobs or "pillows" as more lava emerges from the advancing flow. A lava fountain is a large amount of lava that is thrown up into the air when gas bubbles expand in the melted rock. Most lava fountains range in height from 30 to 300 feet, but it can be as tall as 1,500 feet tall. Lava fountains erupt inside lava lakes, along a fissure, isolated vents or from lava tubes. A lava lake is made when large amounts of lava pour into a crater where it is cooled and dried.

Types of Volcano Eruptions Effusive eruptions are not violent eruptions. Lava pours out onto the ground from a vent and spreads out over the land. Lava in this kind of eruption will be different depending on where the eruption happens and what kind of minerals makes up the lava. A pyroclastic flow is an avalanche of hot ash, pumice, small rock pieces, and gases that flow close to the ground down a volcano. These flows can move 100 kilometers per hour or faster and they can be hotter than 500 degrees centigrade. This hot avalanche burns everything in its path. It also moves fast enough and hard enough to flatten everything in its way. Phreatic eruptions happen when water below the surface of the earth is heated by the magma in the volcano. The water can be so hot that it boils and turns into steam. During this kind of eruption steam, water, ash, blocks, and bombs can explode out of the volcano.

Types of Volcano Eruptions Plinian eruptions are very violent and tephra and gas are thrown high into the air and pyroclastic flows and surges down the side of the volcano. Ejected material such as rock fragments into the atmosphere is known as tephra. Strombolian eruptions cause lava to explode from a vent followed by a flow of lava out of the volcano. Gases inside the volcano build up and then release a spray of lava that turns into a lava flow. The lava flow slows down until the gases build up again. The lava pieces that are thrown out of the volcano are bombs that take on a rounded shape as they fly through the air. Vulcanian eruptions are explosive. New lava fragments fly through the air, but do not become rounded. This is because the lava pieces have cooled off enough for the shape to not change. Breadcrust bombs and blocks are thrown out of the volcano during a vulcanian eruption

Benefits of Volcanic Activity A natural glass that comes from lava is pumice, it is widely used for grinding and polishing metals, stones, and other materials. When lava dries to a rock form, it is commonly used in building roads. Volcanic material is a source of precious gems like Opal. When volcanoes erupt, the lava releases some healthy gases, including carbon dioxide and hydrogen. When oxygen mixes with hydrogen, it creates water vapor and that begins the water cycle. After a volcanic eruption, the burning lava can turn into the some of the richest soil in the world. Some early civilizations grew their food in the rich volcanic soil. Volcanic ash that has been weathered greatly improves soil fertility. Geothermal energy is a useful way to make electricity. With a ready supply of water and a a steady source of heat, steam can be created to power turbines which will spin generators to make electricity. Volcanoes have sometimes very rich amounts of minerals (such as gold, silver, and copper) deep down under a extinct volcano. We can also make industrial products like road-making materials, cleaning products, and other raw chemical or industrial materials. Volcanoes also can bring in tourism. There are many businesses involved in promoting Hawaii Volcano National Park. During some winter days, a person can ski on the slopes of Mauna Kea in the morning (next to the observatories) and surf at the beach in the afternoon. There are many water sports and wondrous hiking trails. The Earth's crust, on which we live and depend, is in large part the product of millions of once-active volcanoes and tremendous volumes of magma that did not erupt but instead cooled below the surface. Hawaii is the only state in the USA built entirely of volcanic materials. The Rotorua-Whakarawarewa area (New Zealand) is known for numerous hot springs, geysers, and other geothermal features that support a significant tourist industry. Calistoga (Napa Valley, California) and mud go way back - Mud baths -- said to relax muscles, sooth aches, improve circulation and smooth the skin.

Hazards of Volcanoes Gases The carbon dioxide the accumulates in soil can kill off trees. Steam and Sulfur dioxide released by the volcano can kill people, plants and animals. Acid rain can kill crops, poison water supplies, and corrode metals. Vog forms a smog of acid rain that causes breathing problems Landslides Gases from inside the magma dissolves into the groundwater making the water acidic and makes the soil weaker, creating a mini-fault zone inside the soil at the top of the volcano. When gravity pulls on the weakened top cone of the volcano a landslide can occur. A lahar (mud flows or debris flows) is a mixture of rapidly flowing rock debris and water that comes from the slopes of volcanoes. They are also known as. They form by the rapid melting of snow and by pyroclastic flows, hard rainfall on loose rock deposits, breakout of a lake dammed by volcanic rock deposits, and by debris avalanches.

Hazards of Volcanoes Lava flows burn and destroy everything in their paths. Basalt flows are thin enough to flow quickly for a long distance. Lava flows made up of andesite move very slowly because it is very thick. A pyroclastic flow is a rapidly moving mass of hot ash, pumice, volcanic gases, and rock fragments that lays low on the ground is called. The temperature can reach 500 degrees or more and it moves fast, 100 kilometers per hour or faster. Anything in the path of a pyroclastic flow is killed. Tephra is made up of fragments of volcanic materials of any size that escapes a volcano during an eruption. It forms into clouds that spread over hundreds of miles, even around the entire world. It can bury an entire city if enough is thrown out of a volcano during an eruption. Volcanoes cause changes in the weather on Earth. Dust clouds from large eruptions block out the sunlight and making the temperature colder. T he gasses and fine dust particles called tephra can drift all the way around the world. This dust veil reflects more sunlight back into outer space and the earth becomes cooler. The cooler temperatures stay around for several years or more.

Four levels of Volcanic Activity and What to do if a Volcano Erupts Active volcanoes erupt constantly. Examples are: Popocatepetl Volcano, Kilauea Volcano, Mount Etna Volcano, Mt. Saint Helens Volcano Intermittent volcanoes erupt fairly regularly. Examples are Mount Asama, Mount Etna, and Hualalai Dormant volcanoes are inactive, but not long enough to determine whether they will erupt again or not. Examples are: Three Sisters (Oregon), Mount Price (British Columbia) and Pelican Butte (Oregon) Extinct volcanoes have been inactive since the beginning of recorded history. Examples are: Diamond Head Hawaii, Humphreys Peak AZ, and Kauai If a volcano erupts: If possible, immediately leave the area. If caught near a stream, beware of mudflows. They can move faster than you can walk or run. Avoid river valleys and low-lying areas. Protect yourself from falling ash by wearing long-sleeved shirts and long pants. Use goggles and wear eyeglasses instead of contact lenses, and wear a dust mask or hold a damp cloth over your face to help with breathing. Stay indoors until the ash has settled. Be sure to close doors, windows, and all ventilation in the house (chimney vents, furnaces, air conditioners, fans, and other vents. Avoid driving, which can stir up volcanic ash that can clog engines, damage moving parts, and stall vehicles. If you have to drive, keep speed down to 35 mi/hr or slower.

The End Volcanoes