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Gravimetry
Gravimetry is the measurement of gravitational acceleration and its variations in space and time, using instruments on the ground, ships, aircraft, or satellites to infer Earth's mass distribution.
Gravity anomaly
A gravity anomaly is the difference between measured gravity, reduced to sea level, and the theoretical gravity of a uniform ellipsoidal Earth, revealing rock density variations.
Gravity gradiometer
A gravity gradiometer is an instrument that measures the rate at which gravity changes from one point to a nearby point, used in resource exploration and passive navigation.
Gravity gradiometry
Gravity gradiometry is a geophysical surveying method that measures how gravitational acceleration changes from point to point, revealing subsurface density structure from aircraft or satellites.
Gravity inversion
Gravity inversion is the geophysical process of estimating a subsurface density model from measured gravity anomalies. It is non-unique and unstable, so regularization and constraints are needed.
Great Artesian Basin
The Great Artesian Basin is Australia's largest groundwater basin, a system of pressurized sandstone aquifers underlying about 1.7 million square kilometers, more than one-fifth of the Australian continent.
Great Blizzard of 1888
The Great Blizzard of 1888, also called the Great White Hurricane, struck the northeastern United States from March 11 to 14, 1888, killing hundreds of people.
Great Blizzard of 1978
The Great Blizzard of 1978 was a severe winter storm that struck the Great Lakes and Ohio Valley on January 26-27, 1978, paralyzing Ohio, Indiana, and Michigan.
Great Frost of 1709
The Great Frost of 1709, known in France as Le grand hiver, was an extraordinarily cold European winter, the coldest on the continent in 500 years.
Great Green Wall
The Great Green Wall is an African Union initiative launched in 2007 to combat desertification in the Sahel, now an 8,000 km restoration mosaic across Africa.
Great Hanshin earthquake (阪神・淡路大震災)
The Great Hanshin earthquake, also known as the Kobe earthquake, was a magnitude 7.3 quake that struck Kobe, Japan, on January 17, 1995, killing 6,434 people.
Great Hurricane of 1780
The Great Hurricane of 1780, also known as Hurricane San Calixto, crossed the eastern Caribbean in October 1780 and remains the deadliest Atlantic hurricane, killing about 22,000 people.
Great Oxidation Event
The Great Oxidation Event, also known as the Oxygen Catastrophe, began roughly 2.4 billion years ago, when oxygen produced by photosynthetic microbes first accumulated in Earth's atmosphere and oceans, permanently changing the planet's surface.
Great Plains low-level jet
The Great Plains low-level jet is a fast southerly airstream in the lower atmosphere over the central United States, most frequent at night in the warm season.
Great Sitkin
Great Sitkin is an active andesitic stratovolcano with a summit caldera on uninhabited Great Sitkin Island in the western Aleutian Islands, Alaska, in continuous eruption since May 2021 with slow lava effusion since July 2021.
Great storm of 1703
The Great storm of 1703 was a violently destructive cyclone that struck southern England and northern France in late November 1703, killing an estimated 8,000 to 15,000 people.
Great storm of 1987
The Great Storm of 1987 was an extratropical cyclone that struck southern Britain and northern France on 15–16 October 1987, felling about 15 million trees.
Green Climate Fund
The Green Climate Fund is a multilateral climate fund created in 2010 under the UNFCCC and headquartered in Songdo, South Korea, to fund low-emission, climate-resilient development in developing countries.
Green flash
The green flash, also called the green ray, is a short-lived green brightening at the upper edge of the Sun at the horizon, usually lasting 1 to 2 seconds.
Green New Deal
The Green New Deal is a family of policy proposals combining deep cuts in greenhouse gas emissions with job creation, best known from a 2019 US congressional resolution.
Green River Formation
The Green River Formation is an Eocene rock unit in Wyoming, Utah, and Colorado, known for exceptionally preserved fossils and the largest oil shale resource on Earth.
Greenbushes Mine
The Greenbushes Mine is a mine in south-west Western Australia that has produced tin, tantalum, and lithium since 1888 and is now a major lithium source.
Greenfield tornado
The Greenfield tornado was a violent EF4 tornado that struck Greenfield, Iowa, on May 21, 2024, killing five people, injuring at least 35, and destroying more than 100 homes.
Greenhouse and icehouse Earth
Greenhouse and icehouse Earth are Earth's two recurring climate states, defined by polar ice, alternating for over 2.5 billion years; Earth is now in an icehouse state.
Greenhouse effect
The greenhouse effect, also called greenhouse warming, warms a planet's surface as gases like water vapor and carbon dioxide absorb infrared radiation, adding about 33 °C on Earth.
Greenhouse gas
A greenhouse gas (GHG) is a gas, such as carbon dioxide, methane, or nitrous oxide, that absorbs infrared radiation and warms Earth's lower atmosphere and surface.
Greenhouse gas emissions
Greenhouse gas emissions, also known as carbon or GHG emissions, are releases of gases like carbon dioxide and methane that warm the atmosphere, reaching 59 GtCO2-eq in 2019.
Greenhouse Gas Pollution Pricing Act
The Greenhouse Gas Pollution Pricing Act is a 2018 Canadian federal statute establishing the federal carbon pricing backstop, upheld by the Supreme Court of Canada in 2021.
Greenland Ice Core Project
The Greenland Ice Core Project (GRIP) was a European project that drilled a 3,029-meter ice core to bedrock at Summit, Greenland, between 1989 and 1992, covering 250,000 years of climate.
Greensand
Greensand, also called glauconitic sandstone, is a typically marine sand or sandstone whose green color comes from glauconite; it is used as fertilizer, water softener, and heavy-metal filter.