geochronology: Quick Facts

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Photos and Videos

Cutaway diagram of a Grand Canyon wall showing layered sedimentary rocks-limestone, shale, sandstone, and composite rocks-with labels indicating Paleozoic rocks (about 252-541 million years old) above older Precambrian rocks, which include Proterozoic (541 million to 2.5 billion years old) and Archean (over 2.5 billion years old) layers. The Colorado River is shown at the base.

Diagram comparing two columns of rock layers, labeled A and B, each containing distinct fossil illustrations at various depths. The matching fossils in corresponding layers show how geologists use fossils to determine the relative ages of rock layers, even when the sections are separated by 200 miles.

Steno, Nicolaus

Diagram explaining Steno's four laws of stratigraphy in geology, with labeled illustrations for the law of superposition, original horizontality, cross-cutting relationships, and lateral continuity, showing how rock layers form and are altered.

The video thumbnail image shows an illustration of the bird dinosaur Longipteryx alongside two toy dinosaur figurines.

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Topics

chronology geologic cycle dating geological record fossil record index fossil historical geology Earth rock geologic time geography geology hydrologic sciences ecology Geoengineering demography cartography Atmospheric science oceanography geomorphology

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mass spectrometry: Geochronology and geochemistry

Key People

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William Lonsdale

British geologist

Steno, Nicolaus

Nicolaus Steno

Danish geologist

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Gerhard, Baron De Geer

Swedish geologist

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Giovanni Arduino

Italian geologist

Cross section of Earth showing the core, mantle, and crust

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