Climate Detective Glossary

abrasion

the mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosion.

biochemical sediments

form from the gradual accumulation of biologic material such as shells or dead plant material.

calving

the process by which an iceberg breaks off from an ice shelf or glacier.

chemical sediments

sediments composed of previously dissolved minerals that have either precipitated from evaporated water or been extracted from water by living organisms and deposited when the organisms died or discarded their shells.

climate

a region's long-term, average weather elements such as temperature and precipitation. The climate generally determines what kind of plants will grow in that region.

clastic sediments or clastic rocks

sediments or rocks composed of fragments, or clasts of pre-existing minerals and rock. A clast s a fragment of geological detritus, chunks and smaller grains of rock broken off other rocks by physical weathering.

cryosphere

the set of all locations on or beneath Earth's surface where frozen water exists.

deformation

an alteration of the size or shape of rocks. Deformation is caused by stress, the scientific term for force applied to a certain area.

delta ¹⁸O record

a synonym for the ratio of ¹⁸O to ¹⁶O.

diatoms

microscopic unicellular marine or freshwater colonial alga having cell walls impregnated with silica.

dropstones

isolated fragments of rock found within finer-grained water-deposited sedimentary rocks. They range in size from small pebbles to boulders.

erosion

the wearing away of land surface by wind or water, intensified by land-clearing practices related to farming, residential or industrial development, road building, or logging.

eccentricity

a measure of how an orbit deviates from circular. A perfectly circular orbit has an eccentricity of zero; higher numbers indicate more elliptical orbits

exhumation

the uncovering or exposure through erosion of a former surface, landscape, or feature that had been buried by subsequent deposition.

forminifera (or forams)

a type of zooplankton, a single-celled marine organism.

evaporite

sedimentary rock formed by evaporating sea water.

glacier

a mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer; many believe that a glacier must show some type of movement; others believe that a glacier can show evidence of past or present movement.

glacial erratics

a piece of rock that differs from the size and type of rock native to the area in which it rests. They are carried by glacial ice, often over distances of hundreds of kilometers and range in size from pebbles to giant boulders.

glaciation

process of becoming covered in glaciers

half life

the time it takes for half the atoms in a radioactive substance to decay.

ice age

a cold period marked by episodes of extensive glaciation alternating with episodes of relative warmth.

iceberg

a piece of ice that has broken off from the end of a glacier that ends in water.

ice-rafted debris

when icebergs melt a certain amount of drifting, sediments of different sizes are deposited onto the bottom of the ocean. These pieces of sediment are normally larger than the surrounding fine-grained mud found there.

ice sheet

a dome-shaped mass of glacier ice that covers surrounding terrain and is greater than 50,000 square kilometers (12 million acres). e.g., the Greenland and Antarctic ice sheets.

ice shelf

a portion of an ice sheet that spreads out over water.

index fossil

a fossil of an organism, known to have existed for a relatively short period of time, used to date the rock in which it is found.

interglacial period

a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age.

isotope

one of two (or more) atoms of the same element which only differ in the number of neutrons found within its nucleus. e.g. H¹ (no neutrons) and H² (1 neutron), H³ (2 neutrons)

lithology

the mineralogy, grain size, texture, and other physical properties of granular soil, sediment, or rock.

magnetometer

a device used for measuring intensity of a magnetic field.

Milankovitch cycles

long-term variations in the orbit of the Earth which result in changes in climate over periods hundred of thousands of years and are related to ice age cycles.

microfossil

a fossil that must be studied microscopically.

moraines

a heap of stones and other types of sediment left by a glacier.

normal polarity

periods of time in the past in which the direction of the Earth's magnetic field was the same as the present direction.

obliquiity

an astronomical term describing the angle of tilt of the Earth's axis of rotation.

paleomagnetism

the fixed orientation of a rock's crystals, based on the Earth's magnetic field at the time of the rock's formation, that remains constant even when the magnetic field changes over time.

paleontologist

a geologist who researches geological periods through the study of fossils.

pH

range of numbers expressing the relative acidity or alkalinity of a solution. In general, pH values range from 0 to 14.

phytoplankton

microscopic floating plants, mainly algae, that live suspended in bodies of water and that drift about because they cannot move by themselves or because they are too small or too weak to swim effectively against a current.

plucking

a glacial phenomenon that is responsible for the erosion and transportation large blocks of bedrock. As a glacier moves down a valley, friction causes the ice at the bottom of the glacier to melt and infiltrate joints in the bedrock.

pollen

a fine powder produced by flowers that fertilizes other plants for reproduction.

precession

the slow, conical motion of the Earth's axis of rotation, caused by the gravitational attraction of the sun and moon.

principle of superposition

the scientific law stating that in any unaltered sequence of rock layers, each layer is younger than the one beneath it and older than the one above it, so that the youngest layer will be at the top of the sequence and the oldest at the bottom.

proxy data

a past climate record like ice cores and tree rings used to interpret paleoclimate. Organisms, such as diatoms, forams, and coral serve as useful climate proxies.

radiolarians

protozoa with amoeba-like bodies and radiating filamentous pseudopods (latin for false feet).

reverse polarity

periods of time in the past in which the Earth's magnetic field was in the opposite direction from the present orientation.

rock flour

finely powdered rock produced as a result of glacial erosion or by artificial grinding.

sedimentation rate

the time it takes for a certain amount of sediment to be deposited on the sea floor (cm/year).

sedimentologist

a branch of geology that encompasses the study of modern sediments such as sand, mud (silt), and clay, and the processes that result in their deposition.

sediments

soil, sand, and minerals washed from land into water, usually after rain.

smear slides

a sample of sediment prepared by taking a small amount of it with a toothpick and mixing it with a few drops of distilled water before it is spread on a glass slide for observation.

strata

distinct horizontal layers in geological deposits. Each layer may differ from adjacent layers in terms of texture, grain size, chemical composition, or other geological criteria.

stratigraphy

a branch of geology which treats the formation, composition, sequence and correlation of the layered rocks as parts of the Earth's crust.

terrane

a group of rocks having a common age or origin.

thrust fault

a thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata.

turbidity current

a current of rapidly moving, sediment-laden water moving down a slope through water, or another fluid. The current moves because it has a higher density than the fluid through which it flows—the driving force of a turbidity current derives from its sediment, which renders the turbid water denser than the clear water above.

weather

the state of the atmosphere at a given location and time. It includes such variables as temperature, precipitation, cloudiness, wind speed and direction, and relative humidity.

weathering

the process by which exposure to atmospheric agents, such as air or moisture, causes rocks and minerals to break down. This process takes place at or near the Earth's surface.

zooplankton

Small (often microscopic) free-floating aquatic plants or animals.