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Hecla Mining
Hecla Mining Company is an American mining company based in Coeur d'Alene, Idaho. Founded in 1891, it is the largest silver producer in the United States and Canada.
Heinrich events
Heinrich events are episodes of massive iceberg discharge into the North Atlantic during the last glacial period, named for Hartmut Heinrich, who documented their sediment layers in 1988.
Hekla
Hekla is an active stratovolcano in southern Iceland, standing 1,490 m high and among the country's most active, erupting 23 times in historical time, most recently in 2000.
Heliotrope (mineral)
Heliotrope, also called bloodstone, is a dark green variety of chalcedony spotted with red iron-oxide markings resembling drops of blood, long used for seals and signet rings.
Hell Creek Formation
The Hell Creek Formation is a rock unit in Montana, Wyoming, and the Dakotas famous for its dinosaur fossils, including Tyrannosaurus rex, and preserving the Cretaceous–Paleogene extinction boundary.
Hematite
Hematite is an iron oxide mineral, Fe₂O₃, and the most important ore of iron; most formed in Precambrian banded iron formations, and it also occurs on Mars.
Hemlo Gold Mine
The Hemlo Gold Mine is a gold mine 35 km east of Marathon, Ontario, one of Canada's largest lode gold deposits, producing about 25 million ounces of gold.
Hemphillian
The Hemphillian is a North American Land Mammal Age, from about 9.0 to 4.9 million years ago, defined by its mammal fauna rather than the standard geologic time scale.
Henderson molybdenum mine
The Henderson molybdenum mine is an underground block-cave mine beneath Red Mountain in Clear Creek County, Colorado, opened in 1976 and owned by Climax Molybdenum.
Herkimer diamond
The Herkimer diamond, also called Little Falls Diamond, is a doubly terminated quartz crystal found in Herkimer County, New York; it is quartz, not true diamond.
Hesperian (Mars)
The Hesperian is the middle of Mars's three geologic epochs, spanning roughly 3.7 to 3.0 billion years ago and marked by outflow channels carved by catastrophic floods.
Hessdalen lights
The Hessdalen lights, also called the Hessdalen phenomenon, are recurring unexplained balls of light of varying shapes and colors in the Hessdalen valley of central Norway, reported since the 1940s.
Heterogenite
Heterogenite is a cobalt oxyhydroxide mineral, CoO(OH), the most abundant oxidized cobalt mineral and principal cobalt ore in the Katanga Copperbelt of the Democratic Republic of Congo.
High Resolution Model Intercomparison Project
The High Resolution Model Intercomparison Project (HighResMIP) was a CMIP6-endorsed project that applied, for the first time, a multi-model approach to studying horizontal resolution in global climate models.
High tide water
High tide water (high water, German Tidehochwasser) is the water level at a tide's highest point. Most coasts see two high tides per 24 h 50 min tidal day; spring and perigean tides raise the highest levels.
High-altitude balloon
A high-altitude balloon, also called a stratospheric balloon or stratostat, is an unpowered lighter-than-air craft carrying instruments into the stratosphere, typically reaching 20 to 40 kilometers.
High-nutrient, low-chlorophyll region
A high-nutrient, low-chlorophyll (HNLC) region is an open-ocean area where surface waters hold plentiful nitrate and phosphate year-round, yet phytoplankton stays scarce, chiefly because iron is depleted.
High-pressure area
A high-pressure area, also known as an anticyclone or high, is a region where surface pressure exceeds that of surrounding air, bringing sinking air, light winds, and dry, settled weather.
High-Resolution Rapid Refresh
The High-Resolution Rapid Refresh (HRRR) is a NOAA numerical weather prediction model that runs hourly at 3-km resolution across the United States, operational since 2014.
Highest temperature recorded on Earth
The highest temperature recorded on Earth is 56.7 °C (134 °F), measured at Furnace Creek Ranch in Death Valley, California, on 10 July 1913, though a 2025 reanalysis contests it.
Highland
A highland is a broad elevated region of hills, mountains, or plateau standing above surrounding lowland; no universal altitude defines it, only elevation, relief, and contrast with neighboring lowlands.
Highstand systems tract
The highstand systems tract (HST) is, in sequence stratigraphy, the upper tract of a sequence, deposited when high, slowly rising sea level lets sediment supply outpace accommodation.
Hikurangi subduction margin
The Hikurangi subduction margin is the plate boundary off New Zealand's East Coast where the Pacific plate subducts beneath the Australian plate, a major earthquake and tsunami hazard source.
Himawari-8
Himawari-8 is a Japanese geostationary meteorological satellite launched in 2014 and operated by the Japan Meteorological Agency, observing East Asia and the western Pacific with a 16-band imager.
Himawari-9
Himawari-9 (ひまわり9号) is a Japanese geostationary weather satellite operated by the Japan Meteorological Agency, launched in 2016 and Japan's primary observation satellite since December 2022.
Hindcasting
Hindcasting, known in geosciences as reforecasting, runs a predictive model over a past period and compares its output with withheld observations to estimate forecast skill.
HIRLAM
HIRLAM, the High Resolution Limited Area Model, is a numerical weather prediction system run by the meteorological services of ten European countries, first operational in 1990.
Hishikari Mine
Hishikari Mine (菱刈鉱山) is an underground gold mine in Isa, Kagoshima Prefecture, Japan, owned by Sumitomo Metal Mining. Discovered in 1981, it is Japan's only commercial-scale metal mine.
Historical climatology
Historical climatology is the study of past climate using documentary evidence such as annals, diaries, and ship logbooks, pioneered by Hubert H. Lamb and complementing natural proxies like tree rings.
History of climate change science
The history of climate change science traces how researchers moved from nineteenth-century ice age puzzles and heat-trapping gases to modern assessments of human-caused global warming.