Volcanoes - Chapter 3 Flashcards
Volcanic plugs
Tall pillar of igneous rock that remains when a volcanic cone is eroded away. Represents the lava that solidifies within the vent
Eg. Puy in France
Volcanic explosivity index
Scale to measure the force of a volcanic eruption. Uses height of ash cloud and amount of ash produced to rank eruptions from 1-8
Volcanic domes
Upturned bowl shaped mound of acidic lava that builds up to form a cone with steep convex slopes or a dome within the crater
Volcanic bombs
Large rocks thrown out of a volcano during an eruption
Volcanic cone
Mountain formed by the eruption and built up of layers of lava and ash
Vent
Hole in the ground from where lava erupts to form a volcanic cone
Tephra
Build up of pyroclastic material such as pumice and ash
Shield volcano
Volcano with gentle, concave slopes and a wide base. Formed by eruption of basic lava
Eg. Mauna Lao, Hawaii
Pyroclasts
Hot ash and rock ejected from a volcano
Pumice
Grey rock full of holes (porous) that form when frothy lava solidifies trapping air bubbles. So light is can float on water
Pyroclastic flow
Heavy mix of hot lava blocks, pumice, ash and gas. Very destructive. Moves at high speeds down slopes typically following valleys
Plutonic landforms
Underground landforms made by intrusion of igneous rock into the crust
Eg. Batholiths
Plateau
Area of flat high ground often with steep sides
Metamorphic aureole
Area of rock surrounding an igneous intrusion that has been changed by heat and pressure from the hot magma
Lapolith
Bowl shaped layer of magma that is injected between 2 layers of sedimentary rock. Weight causes underlying rock layers to bed downwards
Eg. Bushveldt lapolith in South Africa
Lava plateau
Steep sided, flat, wide surface that forms when lava comes out of the ground and separates out. layers of lava can build up to form the lava plateau
Eg. The Giants Causeway
Lava
Molten rock that erupts from a volcano
Lahar
Type of mud flow triggered by a volcanic eruption. Composed of ash, rocky debris and water. Flows down volcano typically along a river valley
Laccolith
Layer of magma that has been injected between 2 layers of sedimentary rock. pressure of magma is so high overlying strata forces up giving laccolith dome like form with a generally flat base
Eg. North Dakota
Fissure
Long deep crack in earths surface from which lava can escape
Extrusive
Igneous rock and volcanic cones that form on the surface when lava erupts and cools quickly
Extinct Volcano
Volcano that hasn’t erupted in last 10,000 years and not expected to erupt again
Eg. Slemish, Antrim
Dykes
Wall of basalt cutting across sedimentary rock layers. Form when sheets of lava pass through cracks in rock and solidify
Dormant volcano
Volcano that is expected to erupt again
Eg Mount Fuji, Japan
Crater
Hollow at the top of a volcanic cone
Caldera
Large volcanic depression. Type of volcanic crater formed by collapse of an empties magma chamber. Formed by big explosive eruptions
Eg. Crater Lake, Oregon
Batholith
Large boy of igneous rock injected into crust that cools and solidifies deep underground
Eg. Leinster Batholith
Basic lava
Lava with low silica content of 55% or less. Runny and flows for many kilometers
Active volcano
A volcano that is currently erupting or has had at least 1 eruption in the last 10,000 years
Eg. Mt. Stramboli
Acidic lava
Lava with high silica content of 70% or more. Very sticky and doesn’t flow very far, forms steep sided domes
Eg. Mount St Helens
