GG103 Nasir Gadzar http://pubs.usgs.gov/gip/hazards/mauna-loa.html http://pubs.usgs.gov/gip/hazards/maunakea-kohala.html http://pubs.usgs.gov/gip/hazards/hualalai.html http://pubs.usgs.gov/gip/hazards/kilauea.html Mahukona Loihihi • Volcanoes Defined • Types of Volcanoes • Volcanoes of the island of Hawaii –Descriptions –Images • Presentation Summary Volcanoes Defined • vol·ca·no n. pl., vol·ca·noes or vol·ca·nos. Abbr. vol. • 1. a. An opening in the earth's crust through which molten lava, ash, and gases are ejected. b. A similar opening on the surface of another planet. • 2. A mountain formed by the materials ejected from a volcano. Types of Volcanoes • Geologist categorize volcanoes into four groups. 1)Composite 2)Cinder 3)Shield 4)Lava domes Composite Volcanoes • Called “composite” because they are made of alternating layers of lava and rock. • Oftentimes called “Stratovolcanoes” • Physical Characteristics – – – – Steep Symmetrical cone shaped Often have snowcapped tops Explosive eruptions Examples of Composite volcanoes Mount Ranier, Washington, USA Mount Fuji, Honshu, Japan Cinder Volcanoes • Simplest type of volcano • Built from particles globs of coagulated lava expelled from a solitary vent which then falls and solidifies around the vent to form a circular cone. • Physical Characteristics – Bowl shaped crater – Size is usually about 1000ft. The size of a hill. – Single vent Example of Cinder cone volcanoe Parícutin volocano, Mexico Lava domes • Also known as “volcanic domes” • Usually occur on flanks of composite volcanoes • Formed by bulbous masses of lava too viscous to flow any great distance, eventually piles around vent and dome becomes bigger from acitivity within. • Physical Characteristics – Rounded – Steep sided Example of Lava dome Unzen lava dome, Japan Shield Volcano • Built almost entirely of fluid lava flows. Flow pours out in all directions from a central summit vent, or group of vents, building a broad, gently sloping cone of flat, domical shape, that profiles a warrior shield. • built up slowly by the accretion of thousands of highly fluid lava flows called basalt lava that spread widely over great distances, and then cool as thin, gently dipping sheets. Lavas also commonly erupt from vents along fractures (rift zones) that develop on the flanks of the cone. Shield Volcano facts • 3-4 miles in diameter but heights of 1500-2000 feet. • The Hawaiian Islands are composed of linear chains of these volcanoes. • Shield Volcanoes of the Island of Hawaii – – – – – Kilauea Mauna Loa Mauna Kea Hualalai Kohala • Southernmost shield volcano on the Big Island. • Predominantly erupts basaltic lava in profuse eruptions. • Kilauea stands just under 4200 feet tall at it's highest point. • Kilauea has a 165m deep circular caldera at its summit that measures 3x5km. • At 60 miles long and 30 miles wide, it makes up half of the entire island. • Mauna Loa is the largest active volcano in the world. • The thickness of its lava pile from the center of the volcano from is 56,080 ft (17,170 m). • Tallest volcano on the Island of Hawaii. • Tallest mountain in the world. • From sea floor to summit it towers more than 5.6 miles (9 km). • Mauna Kea is the only Hawaiian volcano known to be glaciated. • The most recent eruption was about 3,500 years ago. Mauna Kea is considered a dormant volcano. Cinder cone on top of Mauna Kea • The summit of Hualalai rises to an elevation of 2523m (8271ft) above sea level. • Hualalai is well-known in Hawaii as a good source for mantle xenoliths. • The surface of Hualalai is entirely composed of post-shield alkalic basalts. • The last historical eruption at Hualalai ended in 1801. This eruption produced very fluid, high velocity lava flows that entered the ocean off western Hawaii. • Presently, the volcano is mantled by alkalic lavas erupted during the post-shield stage of volcanism. • Summit elevation of 1700 m (5577ft.) • Kohala is considered to be extinct because it has not erupted for 60,000 years. • Kohala is the oldest of the sub-aerial volcanoes that make the Island Of Hawaii. • Volcanoes are openings in the earth's crust through which molten lava, ash, and gases are ejected. • There are four categories of volcanoes 1) Composite 2) Cinder 3) Lava dome 4) Shield • Volcanoes found in the island of Hawaii are Shield volcanoes, these volcanoes names are: Kilauea, Mauna Loa, Mauna Kea, Hualalai, and Kohala. Mahukona is a seamount in west.