Volcanoes Vocabulary Dr. Cyndi Orsburn

Volcanoes Vocabulary Aa- (pronounced ah'-ah) a type of lava that forms a thick, rough crust Active volcano- a volcano that has erupted in the past 10,000 years, may be currently erupting, and is expected to erupt again Ash - Measurement of particle size applied to the finest pyroclastic material, fragments less than 0.08 inches (2mm) in diameter, blasted into the air by volcanic explosions. Basalt - Volcanic rock poor in silica but rich in magnesium, iron, and calcium. The most common volcanic rock. Basin: A broad bowl-shaped valley Base surge - Turbulent low-density cloud of gas with suspended solid debris that expands radially outward from the base of an eruption column. Comparable to the ring that forms at the base of the cloud formed by a nuclear explosion. Batholith: When large amounts of magma harden in the crust

Volcanoes Vocabulary Bomb - Fragment of magma varying in diameter from a few inches to several feet ejected into the air during a volcanic explosion (see tephra) Caldera- a large, cauldron-shaped depression caused by the collapse of the ground when the magma chamber is empty Cinder cone volcano- the most common and smallest type of volcano, usually not more than 300 m (1000 ft) tall, produced by pyroclastic flows. An example of a cinder cone volcano is Paricutin in Mexico. Cinders--Smaller pieces of debris too small to be called a "bomb." Composite volcano- also known as stratovolcano, formed by a combination of lava flows and pyroclastic explosions that form alternating layers. Composite volcanoes are steep and often very tall. Examples of composite volcanoes are Mt. Fuji in Japan, Mt. Kilimanjaro in Tanzania, and Mt. Rainier in Washington. Conduit - Passageway, more or less cylindrical in shape through which magma rises from the magma chamber to the surface during volcanic activity. Crater- an indentation at the top of a volcano

Volcanoes Vocabulary Dike: Magma that forces itself against rock layers Dormant volcano- a volcano that is not currently erupting, but is expected to 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. Extinct volcano- a volcano that has not erupted in the past 10,000 years, and is not expected to erupt again Fissures - fractures or cracks on the slopes of a volcano. Geyser: A fountain of water and steam that erupts from the ground Hot spots- volcanically active places that lie above mantle plumes

Volcanoes Vocabulary Intrusion: Forms when magma hardens underground to form igneous rock Island arc- a chain of volcanic islands created when a tectonic plate passes over a hot spot. The Hawaiian Islands are an example of an island arc. Lahar- a fast-moving volcanic mudflow composed of ash and water Lapilli- intermediate-sized fragments of material (2-64 mm, or 0.08-2.5 in) that are ejected in a pyroclastic explosion Lava- magma that reaches Earth's surface Lava flow the outpouring of lava onto the land from a vent or fissure Lava lake - Lake of molten lava inside a crater tens or hundreds of feet in diameter. Such lakes can remain active for many years. Lava Plateau - A wide, flat surface formed when lava is expelled from long narrow openings in the crust and spreads rapidly. Layers are formed by multiple eruptive events.

Volcanoes Vocabulary Lava tube a tunnel formed when the surface of a lava flow cools and solidifies while the still-molten interior flows through and drains away. Magma- molten rock below Earth's surface Magma chamber- a large area deep underground filled with magma Mantle plume- a column of hot rock that rises up to the surface from Earth's interior Obsidian is volcanic glass. Obsidian cools so quickly that it doesn't have time to crystallize. Pacific Ring of Fire --The ring of volcanoes that circle the Pacific Ocean from the tip of South America, along the west coast of the U.S., through Pahoehoe- (pronounced pah-hoy-hoy) a type of lava that forms a thin, ropy crust when it hardens Plate tectonics - a theory that explains that the Earth's crust is divided into approximately 12 major plates that fit together like a giant jigsaw puzzle. Pillow lava- a smooth, rounded type of lava flow that erupts underwater

Volcanoes Vocabulary Pipe: A long tube in the ground that connects the magma chamber to earth's surface Pumice - Frothy volcanic rock heavily vesicled formed by the expansion of gas in erupting lava Pyroclastic flow- a high-temperature mixture of hot ash and fragments of lava that erupts with great force and speed. Pyroclastic flows are the most dangerous type of volcanic eruptions, traveling at speeds of up to 200 km/hr (125 mph) with temperatures of up to 700 degrees C (1300 degrees F). Rift zone - a crack in the Earth's surface where volcanic eruptions occur. Scoria - Dark, vesicled volcanic rock produced by moderately explosive activity or lava flows and resulting from blobs of gas-charged lava that have cooled in flight. Shield volcanoes- volcanoes that form from fluid lava that builds up slowly over time, creating a wide, gently-sloping mountain shaped like a warrior's shield. Examples of shield volcanoes are Kilauea and Mauna Kea in Hawaii Silica: A mixture of silicon and oxygen

Volcanoes Vocabulary Sill: When magma squeezes between horizontal layers of rock Submarine volcano - volcano below sea level. Tephra- any material ejected during a pyroclastic explosion, regardless of size Vent- an opening at the top or side of a volcano where lava erupts VOG - A blended word derived from the words volcanic and smog. VOG is formed by sulfur dioxide (and other gases) that mix with oxygen and moisture in direct sunlight during volcanic activity. Volcano --A mountain composed of cooled lava built up by repeated eruptions Volcanic neck: Formed when magma hardens in a volcano's pipe