1. Volcanoes. A volcano is a landform (usually a mountain) where molten rock erupts through the surface of the planet.

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1 1. Volcanoes A volcano is a landform (usually a mountain) where molten rock erupts through the surface of the planet. In simple terms a volcano is a mountain that opens downward to a pool of molten rock (magma) below the surface of the earth. It is a hole in the Earth from which molten rock and gas erupt. The name "volcano" has its origin from the name of Vulcan, a god of fire in Roman mythology. As pressure in the molten rock builds up it needs to escape somewhere. So it forces its way up fissures which are narrow cracks in the earths crust. Once the magma erupts through the earth s surface it s called lava. There are around 1510 'active' volcanoes in the world. We currently know of 80 or more which are under the oceans. An earthquake occurs when two plates pushing past each other cause a fracture in the Earth s crust Lava and Magma Magma is liquid rock inside a volcano. Lava is liquid rock (magma) that flows out of a volcano. Fresh lava ranges from 1,300 to 2,200 F (700 to 1,200 C) in temperature and glows red hot to white hot as it flows Three layers the Earth 1. Crust The crust is the outer layer of Earth. It is about 18 miles thick. It is the part we live on. 2. Mantle The second layer is called the mantle. It is about 1,800 miles thick. 3. Core The inner layer is called the core. The earth is divided into three main layers a hard outer crust, a soft middle crust, and a center core. The outer crust is broken into massive irregular pieces called plates. These plates are moving very slowly, driven by energy forces deep within the earth. Earthquakes occur when these moving plates grind and scrape against each other.

2 1.3. Causes of volcano eruptions and Earthquakes The Earth's crust is made up of huge slabs called plates, which fit together like a jigsaw puzzle. These plates sometimes move. These are the Seven Major Plates : 1. Pacific 2. North American 3. South American 4. African 5. Eurasian 6. Antarctic 7. Indo-Australian 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. When magma erupts through the earth's surface it is called lava. Over half of the world s volcanoes arise in a belt around the Pacific Ocean called the Ring of Fire. Types of Plate Boundaries A. Divergent - Spreading Center - Constructive Margin. Characterized by ocean ridges and sea floor spreading.

3 B. Convergent - Characterized by trenches and island arcs 1. Ocean - Ocean (Japanese Islands) 2. Ocean - Continental (Cascade Mountains) 3. Continent - Continent (Himalayas) C. Transform - Plates moving past one another along strike- slip faults.

4 2. Volcanic Eruptions As well as the danger from the hot lava, an erupting volcano can trigger are life threatening things. tsunamis flash floods earthquakes mud flows rock falls Effect of Volcanoes on people and the environment Volcanoes can have a very serious effect on the lands and people around them when they erupt. Buildings are destroyed and people are made homeless. People are killed. Clouds of ash cover plants making them inedible. Poisonous gases kill people and animals. Dust causes pneumonia and illnesses to the survivors. Dark skies, severe winds and heavy rains may follow an eruption for months afterwards People living within Volcanoes and Earthquakes One in 10 people in the world live within 'danger range' of an active volcano.

5 People can get used to living near a volcano, but it is always a little dangerous. Scientists have estimated that at least 200,000 persons have lost their lives as a result of volcanic eruptions during the last 500 years. People set up homes on the slopes of volcanoes because of the rich, fertile soil produced. Earthquakes can be a warning of volcanoes. Earthquakes can happen days or hours before a volcanic eruption happens. They both have to do with Tectonic plates and they are both can be very destructive. Earthquakes along with volcanoes can cause deaths and loss of homes. 3. The different parts of a Volcano The image below shows the different parts of a volcano. Definitions Magma - Molten rock beneath Earth's surface. Parasitic Cone - A small cone-shaped volcano formed by an accumulation of volcanic debris. Sill - A flat piece of rock formed when magma hardens in a crack in a volcano. Vent - An opening in Earth's surface through which volcanic materials escape. Flank - The side of a volcano. Lava - Molten rock that erupts from a volcano that solidifies as it cools. Crater - Mouth of a volcano - surrounds a volcanic vent.

6 Conduit - An underground passage magma travels through. Summit - Highest point; apex Throat - Entrance of a volcano. The part of the conduit that ejects lava and volcanic ash Ash - Fragments of lava or rock smaller than 2 mm in size that are blasted into the air by volcanic explosions. Ash Cloud - A cloud of ash formed by volcanic explosions. 4. Types of Volcanoes and the Shapes of Volcanoes 4.1. Types of Volcanoes There are 3 different types of volcanoes: 1. Active - eruptions can be anytime and often. 2. Dormant - has been a while since it has erupted, but could at anytime. 3. Extinct, meaning it hasn't erupted in a very long, long time so it probably won't ever again Shapes of Volcanoes The type of magma in the earth creates four different types volcanoes: shield volcanoes composite volcanoes cinder cones lava domes Shield Volcano flat If the magma is runny, the gas can escape easily and there will not be an explosion. The magma just comes out of the mountain and flows down the sides. Shield volcanoes are shaped like a bowl or shield in the middle with long gentle slopes made by the lava flows. Examples include the volcanoes in Hawaii and Mount Etna.

7 Composite Volcano - tall and thin If the magma is thick and sticky (like honey), the gas cannot escape, so it builds up and up until it explodes sending out huge clouds of burning rock and gas. Composite volcanoes are steep-sided volcanoes composed of many layers of volcanic rocks, usually made from thick sticky lava, ash and rock debris (broken pieces). Composite volcanoes are also known as strato-volcanoes. Examples include Mount Fuji in Japan, Mount Cotopaxi in Ecuador, Mount Shasta and Lassen in California, Mount Hood in Oregon, Mount St. Helens and Mount Rainier in Washington and Mt. Etna in Italy 4.3. Cinder cones Cinder cones are circular or oval cones built from erupting lava that breaks into small pieces as it shoots into the air. As small pieces fall back to the ground, they cool and form cinders around the vent Lava domes Lava domes are formed when erupting lava is too thick to flow and makes a steep-sided mound as the lava piles up near the volcanic vent.

8 5. Volcano Vocabulary Active volcano: A volcano that is erupting or has erupted within historical time and is considered likely to do so in the future. Ash: Fine particles of rock dust blown from an explosion vent. Ashfall: Volcanic ash that has fallen through the air from an eruption cloud. Vent : A vent is an opening at the Earth's surface of a volcanic conduit. Composite Volcano: A steep volcanic cone built by both lava flows and pyroclastic eruptions. Compound Volcan: A volcano that consists of a complex of two or more vents, or a volcano that has an associated volcanic dome, either in its crater or on its flanks. Examples are Vesuvius and Mont Pelee. Conduit: A passage (pipe) followed by magma in a volcano. Crater: A steep- sided, usually circular depression formed by either explosion or collapse at a volcanic vent. Dormant volcan: A volcano which is presently inactive but which may erupt again. Eruption: The process by which solid, liquid, and gaseous materials are ejected into the earth's atmosphere and onto the earth's surface by volcanic activity. Fault: A crack or fracture in the earth's surface. Fissures: Elongated fractures or cracks on the slopes of a volcano. Geysers: Springs that throw boiling water high in the air. They are caused by volcanic heat warming trapped ground water. Hot Spot: A volcanic center, 60 to 120 miles across and persistent for at least a few tens of million of years, that is

9 thought to be the surface expression of a persistent rising plume of hot mantle material. Lava: Magma which has reached the surface through a volcanic eruption. Streams of liquid rock that flow from a crater or fissure. Lava Flow: An outpouring of lava onto the land surface from a vent or fissure. Magma: Molten rock beneath the surface of the earth. Magma chamber (Magna reservoir): The subterranean cavity containing the gas- rich liquid magma which feeds a volcano. Mantle: T he zone of the earth below the crust and above the core. Ring of Fire: The regions of mountain- building earthquakes and volcanoes which surround the Pacific Ocean. Stratovolcano: A volcano composed of both lava flows and pyroclastic material. Vent: The opening at the earth's surface through which volcanic materials issue forth. Volcanic eruption: When hot rocks and lava burst from a volcano. Volcano: A vent in the surface of the Earth through which magma and associated gases and ash erupt; also, the form or structure, usually conical, that is produced by the ejected material. Vulcan: Roman god of fire and the forge, after whom volcanoes are named Elastic Rebound Theory 6. E arthquakes Elastic Rebound Theory E xplains how energy is stored in rocks 1. Rocks bend until the strength of the rock is exceeded 2. Rupture occurs and the rocks quickly rebound to an undeformed shape

10 3. Energy is released in waves that radiate outward from the fault The Focus and Epicenter of an Earthquake The point within hypocenter. The point epicenter. Earth directly where above the faulting focus begins on the is the focus, surface is or the Seismographs record earthquake events Where Do Earthquakes Occur and How Often? 80% of all earthquakes occur in the circum-pacific belt most of these result from convergent margin activity ~15% occur in the Mediterranean-Asiatic belt remaining 5% occur in the interiors of plates and on spreading ridge centers

11 more than 150,000 quakes strong enough to be felt are recorded each year