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Dissolved inorganic carbon
Dissolved inorganic carbon (DIC) is the total inorganic carbon dissolved in seawater, mainly bicarbonate, carbonate, and carbon dioxide, and is the route by which human-made CO₂ enters the ocean.
Dissolved organic carbon
Dissolved organic carbon (DOC) is the organic carbon in water that passes a 0.45-micrometer filter, making up about 90% of total organic carbon in most waters.
Dissolved oxygen
Dissolved oxygen (DO) is the amount of oxygen gas dissolved in water and available to aquatic organisms, usually reported in mg/L, and a core measure of water quality.
Distributary channel
A distributary channel is a stream branch carrying water and sediment away from a main channel rather than adding to it as a tributary does, forming river deltas.
Divergent boundary
A divergent boundary, also known as a divergent plate or constructive boundary, is where two tectonic plates pull apart and magma rising between them creates new crust.
Dixie Fire
The Dixie Fire was a 2021 wildfire in the northern Sierra Nevada, ignited by a tree contacting a PG&E line, that burned 963,309 acres and destroyed Greenville.
DNAPL
DNAPL (dense non-aqueous phase liquid) is an organic liquid denser than water and only slightly soluble in it; common examples include TCE, PCE, coal tar, and PCB-containing oils.
Dolomite (mineral)
Dolomite, also called pearl spar, is a calcium magnesium carbonate mineral with formula CaMg(CO3)2, one of the three most abundant carbonate minerals alongside calcite and aragonite.
Dolomitization
Dolomitization is the geologic process in which calcite in limestone is converted to dolomite by magnesium-rich fluids, producing dolostone, abundant in rocks older than 100 million years.
Dolostone
Dolostone is a carbonate sedimentary rock with more than 50 percent of the mineral dolomite, usually limestone altered by magnesium-rich fluids; it reacts weakly with dilute acid.
Dome Fuji Station
Dome Fuji Station (ドームふじ基地), Japanese inland Antarctic station at 77°19'S, 39°42'E, 3,810 m in Dronning Maud Land; established 1995 for deep ice-core drilling, producing cores to 720,000 years; year-round operations suspended.
Don't Look Up
Don't Look Up (2021) is Adam McKay's Netflix apocalyptic satire, co-written with David Sirota, starring DiCaprio, Lawrence, and Streep as astronomers warning of a comet; Metascore 49, Best Picture Oscar nominee.
Dona Juana
Doña Juana (Dona Juana) is an active dacitic stratovolcano, 4,160 m, in Nariño, SW Colombia, whose 1897-1936 eruptions killed over 100 people; it is monitored by the SGC from Pasto.
Doppler on Wheels
Doppler on Wheels (DOW) is a network of truck-mounted Doppler weather radars designed by Joshua Wurman and first deployed in 1995 to drive to and scan tornadoes and hurricanes.
Double-diffusive convection
Double-diffusive convection, first called thermohaline convection, arises when a fluid's density depends on two components, like heat and salt, that diffuse at very different rates.
Downburst
A downburst, also known as a Plough Wind, is a strong downdraft from a thunderstorm that strikes the ground and spreads outward as damaging straight-line winds, named by Ted Fujita in 1976.
Downscaling (climate modeling)
Downscaling is a family of techniques that translate coarse global climate model output, on grids of 100 to 300 km, into regional and local climate information for impact and risk assessment.
Downslope windstorm
A downslope windstorm is a period of strong, gusty winds descending the lee side of a mountain range. The warm North American variety is the Chinook wind.
Downward continuation
Downward continuation is a geophysical processing technique that projects potential field data, such as gravity or magnetic anomalies, to a level closer to its sources, enhancing shallow features.
Dragon Bravo Fire
Dragon Bravo Fire was a 2025 lightning-caused wildfire in Grand Canyon National Park. It burned for nearly three months, destroying the Grand Canyon Lodge, and killed one firefighter.
Drainage density
Drainage density is a measure of how finely a landscape is dissected by stream channels: the total stream length in a drainage basin divided by its area, first formalized by Robert E. Horton in 1932.
DRASTIC
DRASTIC is a GIS-based overlay index method that rates seven hydrogeologic factors, named in its acronym, to assess groundwater vulnerability to contamination from surface pollutants.
Dravite
Dravite is a magnesium-rich member of the tourmaline group of minerals, named in the 1880s for the Drava river near its type locality in Slovenia.
Drift (stream ecology)
Drift in stream ecology is the downstream transport of benthic invertebrates in the water column, a primary food source for stream fishes and a means of dispersal.
Drifter (oceanography)
A drifter, also known as a Lagrangian drifter, is a satellite-tracked ocean buoy with a subsurface drogue at 15 m depth that follows currents while measuring temperature and position.
Drill hole surveying and downhole orientation
Drill hole surveying and downhole orientation measure a borehole's inclination and azimuth with depth to reconstruct its three-dimensional path, and determine the in-hole direction of core features.
Dropsonde
A dropsonde is an expendable weather instrument released from aircraft that falls on a parachute, measuring pressure, temperature, humidity, and wind; GPS dropwindsondes have improved tropical cyclone forecasts since 1997.
Drought
A drought is a prolonged absence or marked deficiency of precipitation, affecting an estimated 55 million people each year and causing about USD 307 billion in annual losses.
Drought in Australia
Drought in Australia, also known as the Big Dry, refers to prolonged periods of abnormally low rainfall affecting agriculture and water supplies across the continent.
Dry intrusion
A dry intrusion is a stream of cold, very dry air that descends from the upper troposphere behind a cyclone's cold front, producing the cloud-free dry slot.