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The time required for one-half of the atoms of a radioactive substance to decay.
A measure of a mineral's resistance to scratching. The hardness of a mineral is measured by scratching it against another substance of known hardness.
Headlands are projections of land that stick out into a sea or lake.
An epoch of the Quaternary Period beginning 10,000 years ago and continuing today.
An elongate block of rock uplifted along roughly parallel faults.
A dark, very fine-grained metamorphic rock produced by the recrystallization of a fine-grained rock by heat from a nearby igneous intrusion. From the German, meaning horn rock.
An area of concentrated heat in the mantle that produces magma that rises to the Earth's surface to form volcanic islands. The volcanic activity of the Hawaiian Islands is one example. Hot spots generally persist for millions of years.
The science that deals with water on and beneath the Earth surface.
Literally, "with water". Refers to minerals or other materials which have water as a primary constituent.