Scoria Cone
Volcano Type: Cone shaped hills, small crater at their summit. Contain scorias and larger volcanic bombs. Basaltic scoria
Shield Volcano
Volcano Type: Broad, gently curved slopes, can be small or form huge mountains. Fissures along their summit. Basaltic lava flows
Composite Volcano
Volcano Type: Symmetrical mountains, big crater at the top. Interlayers of lava flows, pyroclastic deposits, and volcanic mudflows.
Volcanic Dome
Volcano Type: Dome shaped features. Consist of solidified lava.Form where felsic or intermediate magma erupts and piles up around a vent
Lava flow
When magma erupts onto the surface and flows away from a vent
Lava dome
A dome shaped mountain or hill of at least partly solidified lava generally of felsic to intermediate composition
Pyroclastic eruption
A volcanic eruption where hot fragments and magma are thrown into the air; also refers to a deposit or rock produced by such an event
Lava fountain
A type of pyroclastic eruption: A fountain of molten lava propelled into the air by pressure and escaping gases
Tephra
A pryoclastic material, regardless of size or origin, ejected during an explosive volcanic eruption; includes ash, pumice, and rock fragments
Volcanic ash
Particles of volcanic tephra that are sand-sized or smaller, and accumulation of such material
Eruption column
A rising column of hot gases, tephra, and rock fragments that erupts high into the atmosphere
Pyroclastic flow
A fast moving cloud of hot volcanic gases, ash, pumice, and rock fragments that generally travel down the flanks of a volcano (aka ash flow). Very dangerous
High viscosity
This kind of viscosity (high or low) prevents gases form escaping easily, so gas builds up and increases the pressure surrounding a rock. This can cause explosive eruptions (felsic, intermediate)
Low viscosity
This kind of viscosity (high or low) allows bubbles to escape relatively easily. Mafic (basaltic)
Basalt
A fine grained, dark colored mafic igenous rock, with or without vesicles and phenocrysts of pyroxene, olivine or feldspar
Basaltic
Type of magma in a shield volcano
Flood basalts
Large volume basaltic lava flows that cover vast areas. Erupt from one or more continuous fissures. Unclear as to where magma originally forms
Volcanic hazard
The existence of a potentially dangerous situation or event, such as a potentially dangerous landslide or a lava flow.
Volcanic risk
An assessment of whether a volcano might have some societal impact
Caldera
A large volcanic depression that is typically circular to elongate in shape and formed by collapse of a magma chamber
Shape, rock type, age and history
Ways to assess how potentially dangerous a volcano is
Seismometer
An instrument that measures group shaking or seismic activity
Volcano
A vent in the surface of Earth through which magma and associated gases and ash erupt; also the form or structure, usually conical, that is produced by material erupted from the vent
Crater
A typically bowl shaped, steep sided pit or depression, generally formed by a volcanic eruption or meteorite impact
Volcanic breccia
A volcanic rock containing angular fragments in a matrix of finer material
Fissure
A magma filled fracture in the subsurface, which typically solodifies into a dike, or a linear volcanic vent erupting onto the land surface
Water, carbon dioxide, sulfur dioxide
Most abundant gases in magma
Vesicular basalt
A basalt that contains vesicles
Nonvesicular basalt
A basalt that does not contain vesicles
Plume
A rising mass of mostly solid material, thought to be the casual mechanism of a hot spot
Proximity, valleys, wind direction
Factors that put areas at the greatest risk of volcanoes
Vesicles
Small holes found in a volcanic rock, representing gas bubbles in a magma that were trapped when the lava solidified
Volcanic bomb
A large rock fragment representing either a large blob of magma or a solid angular block ejected during an explosive volcanic eruption
active, dormant, extinct
Three different states of volcanoes (current, not current but could be, no chance of eruption)
Hydrology
Process of volcanic monitoring: gases get scrubbed out of plume, so can measure steam that comes out of ash
Seismicity
Process of volcanic monitoring: put instruments on volcano and monitor it was afar
Deformation
Process of volcanic monitoring: as magma increases at depth, the pressure expands the size of the volcano
Pumice
A textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. Unusual
Lahars
Mudslides that result from a volcano- melted snow, ice, mud.
Viscosity
The resistance of a gas or liquid to flow
basaltic eruptions (lava fountain), scoria cone, lava flow
Ways the basaltic magma erupts
Lava fountain
Type of basaltic eruption: gases carry bits of lava into the air
Scoria cone
Type of basaltic eruption: pieces of scoria create a cone shaped hills
basaltic lava flow
Type of basaltic eruption: fluid lava pours from the vent and flows downhill
Fissure eruption
Type of shield volcano eruption: Magma rises to the surface and erupts through a fracture
basaltic lava flow
Type of shield volcano eruption: fluid lava pours from the vent and flows downhill
pillow basalt
Type of shield volcano eruption: fluid lava erupts into water
falling objects, gases, volcanic ash
Hazards of scoria cones
eruption beneath the surface melts ice, causes floods
Hazard of basaltic eruptions
generation, rise, eruption formation
Steps of caldera formation
increased gas flow, warming of volcano temperature, ground size expansion
Changes that might indicate a volcanic eruption
Fast moving lava, pyroclastic flows, eruption columns
Type of eruptions from composite volcanoes