Holes and other openings in basaltic flow which are the result of trapped gas bubbles. vesicles are often filled at a later date with a wide variety of materials, including, quartz, agate, zeolite...
An outpouring of lava onto the surface from a vent or fissure. also, a solidified tongue-like or sheet-like body formed by outpouring lava.
An instrument that records seismic waves; that is, vibrations of the earth. used to record and measure earthquakes.
An impermeable geologic formation or stratum which will not hold or transmit fluid.
An igneous rock with mafic composition.
|phreatic eruption (explosion)|
An explosive volcanic eruption caused when water and heated volcanic rocks interact to produce a violent expulsion of steam and pulverized rocks. magma is not involved.
An explosive eruption in which the resultant cloud of hot ash and other material moves laterally rather than upward.
An estimate of the true age of a mineral or rock based on the rate of decay of radioactive minerals.
An eruption from the side of a volcano (in contrast to a summit eruption.)
An elongate crustal block that is relatively depressed (downdropped) between two fault systems.
An underground zone of porous rock containing hot water.
- Angular fragments of material, commonly formed by physical weathering processes or explosive volcanic activity.
- Any stone composed of angular fragments embedded and consolidated in ...
Hawaiian term for a fluid volcanic eruption resulting in broad basaltic shield volcanoes. the highly fluid magma flows readily, and hardens into ropey forms as it cools. it can be very impressive ...
Grooves eroded into bedrock by rock debris frozen into the base of a glacier.
General term for material deposited by a glacier. see also moraine.
General term for material deposited by a glacier.
General term for material deposited beneath, along the sides, and/or at the terminus of a glacier. also, what we get here in oregon during the fall, winter, and spring. see also till.
From the greek "meta" (change) and "morph" (form). commonly occurs to rocks which are subjected to increased heat and/or pressure. also applies to the conversion of snow into g...
- Finely ground rock material, usually associated with glaciers (or faults). can be mixed with water and formed into loaves which, when baked for 45 minutes at 350°, are totally unedible.
Evidence of past life on earth. can include the preserved hard and soft parts of plants and animals, tracks and burrows, whole organisms preserved intact in amber or tar, and fossilized dung. any ...
Erosional features associated with alpine glaciers.
Energy derived from the internal heat of the earth.
A volcano that is not presently erupting and is not likely to do so for a very long time in the future.
A gently sloping volcano in the shape of a flattened dome, built almost exclusively of mafic lava flows. the hawaiian islands are a good example.
- A general term for clay, silt, sand, gravel or similar unconsolidated material deposited by a stream or other body of running water.
- Gravel, sand, silt, soil, or other material that...
- A flowage of water-saturated earth material possessing a high degree of fluidity during movement. a less-saturated flowing mass is often called a debris flow. a mudflow originating on the flan...
A flow of unsorted masses of rock and other material downslope under the influence of gravity. water is commonly involved as a catalyst and/or lubricant. for example
|marker horizon (or bed)|
A distinctive horizon which is used for regional correlation of lithology. a good marker horizon is distinctive, widespread, and represents a relatively short period of geologic time. for example,...
A copmmon mechanical weathering process where rock and debris frozen into the sides and bottom of a glacier act like sandpaper and wear down the bedrock the glacier is mocing across.
A continuous release of seismic energy typically associated with the underground movement of magma. it contrasts distinctly with the sudden release and rapid decrease of seismic energy associated ...
|glacial quarrying (plucking)|
A common mechanical weathering process in alpine glaciated terrain where glacial ice frozen into cracks in the bedrock literally "pluck" rock material from the valley floor.
A combination of snow and rock
A geologic formation or stratum that significantly retards fluid movement.
A large igneous intrusion formed at great depth in the crust.
A volcano that is erupting; or one that, while not erupting at the present, has erupted within (geologically) recent time and is considered likely to do so in the (geologically) near future.
A volcano composed of both lava flows and pyroclastic material. also called "composite" volcanoes. common at convergent boundaries. excellent examples in the u.s. include mt. st. helens,...
A volcanic cone built entirely of loose fragmented material (pyroclastics.)
A vent or opening through which issue steam, hydrogen sulfide, or other gases. the craters of many dormant volcanoes contain active fumaroles.
A turbulent mixture of gas and rock fragments, most of which are ash-sized particles, ejected violently from a crater or fissure. the mass of pyroclastics is normally of very high temperature and ...
A tunnel formed when the surface of a mafic lava flow cools and solidifies, while the still-molten interior flows through and drains away. these can insulate the flow and allow it to travel great ...
A torrential flow of water-saturated volcanic debris down the slope of a volcano in response to gravity. a type of mudflow.
A steep volcanic cone built by both lava flows and pyroclastic eruptions.
A snowball which has been stored in the freezer for several months (or more). useful for surprising unwelcome visitors during the spring and summer months.
A nearly vertical fault with side-slipping displacement.