Science / Geology Glossary

Joint Set: A group of joints that are parallel or nearly parallel. They are frequently formed at the same time interval from a common process.

Jolly Balance: A spring balance used in the determination of specific gravity.

Juvenile Gas: Gases that come to the surface for the first time from the deep interior.

Juvenile Water: Water that is new to the hydrologic cycle. Brought to Earth's surface through volcanic eruptions.

K-Feldspar: A potassium feldspar such as orthoclase, microcline, sanidine or adularia. Also referred to as potash feldspar.

Karst: A landscape that is characterized by the features of solution weathering and erosion in the subsurface. These features include caves, sinkholes, disappearing streams and subsurface drainage.

Kerogen: A mixture of organic substances found in many fine-grained sedimentary rocks and a major constituent of oil shale.

Kettle: A small hollow or depression formed in glacial deposits when outwash was deposited around a residual block of ice that later melted.

Kettle Lake: A lake that forms in a kettle.

Kilobar: A unit of pressure equal to 1000 bars (the mean atmospheric pressure at 100 meters above sea level is one bar).

Kimberlite: A variety of peridotite that is found in volcanic pipes which are thought to be intrusions from the upper mantle. Many diamond deposits are found in kimberlite pipes.

Knickpoint: An abrupt change in slope. A point on a stream profile where a change in gradient occurs. This could be caused by a change in underlying bedrock or bedrock structure.

Knob: A small hilltop that is round in shape.

Laccolith: An igneous intrusion that has been forced between two layered rock units. The top of the intrusion is arched upwards and the bottom of the intrusion is nearly flat.

Lahar: A mudflow composed of water and volcanic ash. Lahars can be triggered by the flash melting of the snow cap of a volcanic mountain or from heavy rain. Lahars are very dangerous because they c . . . View Full Definition

Laminar Flow: A state of uniform flow within a fluid in which the moving particles travel along parallel paths (compare with Turbulent Flow).

Landslide: The rapid downslope movement of soil and rock material, often lubricated by groundwater, over a basal shear zone: also the tongue of stationary material deposited by such an event.

Lapilli: Volcanic rock materials which are formed when magma is ejected by a volcano. Typically used for material that ranges between 2 and 64 millimeters in diameter.

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