Volcano Keywords

1. Keywords: Volcanoes
Hotspot: an unusually warm area found deep within the mantle of the crust.
Fissure: a long crack in the Earth’s surface. Magma erupts from it.
Pyroclastic material: Material that erupts from volcanoes. This includes ash, rock, dust,
lava, gas and bombs (larger pyroclasts)
Pyroclastic flow: the material that flows down the side of a volcano during an eruption.
Lahars and nueés ardentes are examples of pyroclastic flows.
Nueésardentes: Clouds of hot ash and poisonousgases that are ejected from a volcano.
They create glowingavalanches that can travel speeds as high as 200km.
Acidic lava: Lava with a high silica content (over 70%). It is thick and does not flow very
far. Leads to a violent eruption. Dome shaped cones are created.
Basic lava: Low in silica content (55% or less). Runny and flows great distances. Lava
flows quickly and leads to the formation of shield cones.
Pahoehoe lava: Lava with a ropey texture. Runny.
Aa lava: Lumpy textured lava.
Pillow lava: Appears as rounded blobs of lava. Found on the sea floor.
Intrusive structure: Magma does not leave the crust. It forces itself into the rock, cooling
to form a feature. The Leinster Batholith is an example of an intrusive structure.
Sill: Magma forces itself in between layersof sedimentary rock. They form close to the
surface and leave behind a horizontal layer of granite.
Dyke: Magma is injected verticallyinto fissures in a rock. Overtime it widens the
fracture and cools creating a vertical layer of granite.
Laccolith: magma pushes the rock above it upwards.
Lopolith: magma pushed rock underneath it downwards.
Extrusive structures: structurescreated by volcanic activity on the surface of the earth.
Eg: Volcanoes.
Geysers: jets of stream and hot water that leap into the air at regular intervals.
Example: Old Faithful, Yellowstone National Park.
Hot springs: groundwater is heated at great depths and then rises to the surface.
Examples can be found in Iceland.
Black smokers: Look like chimney openings. Found at mid-ocean ridgeswhere water
hotter than 400oC rises out of the mantle.
Tiltmeters: a tool used to predictvolcanic activity. It examines bulging at the side of a
volcano.