Historical geology
Historical geology or palaeogeology is a discipline that uses the principles and methods of geology to reconstruct the geological history of Earth.[1] Historical geology examines the vastness of geologic time, measured in billions of years, and investigates changes in the Earth, gradual and sudden, over this deep time. It focuses on geological processes, such as plate tectonics, that have changed the Earth's surface and subsurface over time and the use of methods including stratigraphy, structural geology, paleontology, and sedimentology to tell the sequence of these events. It also focuses on the evolution of life during different time periods in the geologic time scale.[2]
Historical development
During the 17th century, Nicolas Steno was the first to observe and propose a number of basic principles of historical geology, including three key stratigraphic principles: the law of superposition, the principle of original horizontality, and the principle of lateral continuity.[3]
18th-century geologist
The discovery of radioactive decay in the late 19th century and the development of radiometric dating techniques in the 20th century provided a means of deriving absolute ages of events in geological history.
Use and importance
Geology is considered a historical science; accordingly, historical geology plays a prominent role in the field.[9]
Historical geology covers much of the same subject matter as physical geology, the study of geological processes and the ways in which they shape the Earth's structure and composition. Historical geology extends physical geology into the past.[1]
Methods
Stratigraphy
Layers of rock, or strata, represent a geologic record of Earth's history. Stratigraphy is the study of strata: their order, position, and age.
Structural geology
Structural geology is concerned with rocks' deformational histories.
Paleontology
Fossils are organic traces of Earth's history. In a historical geology context, paleontological methods can be used to study fossils and their environments, including surrounding rocks, and place them within the geologic time scale.
Sedimentology
Sedimentology is the study of the formation, transport, deposition, and diagenesis of sediments. Sedimentary rocks, including limestone, sandstone, and shale, serve as a record of Earth's history: they contain fossils and are transformed by geological processes, such as weathering, erosion, and deposition, through deep time.
Relative dating
Historical geology makes use of relative dating in order to establish the sequence of geological events in relation to each another, without determining their specific numerical ages or ranges.[10]
Absolute dating
Absolute dating allows geologists to determine a more precise chronology of geological events, based on numerical ages or ranges. Absolute dating includes the use of
Plate tectonics
The theory of plate tectonics explains how the movement of lithospheric plates has structured the Earth throughout its geological history.[12]
Weathering, erosion, and deposition
Weathering, erosion, and deposition are examples of gradual geological processes, taking place over large sections of the geologic time scale. In the rock cycle, rocks are continually broken down, transported, and deposited, cycling through three main rock types: sedimentary, metamorphic, and igneous.
Paleoclimatology
Paleoclimatology is the study of past climates recorded in geological time.
Brief geological history
Eon | Era | Period | Epochs | Start |
---|---|---|---|---|
Phanerozoic | Cenozoic | Quaternary | Holocene | 0.0117 |
Pleistocene | 2.558 | |||
Neogene | Pliocene | 5.333* | ||
Miocene | 23.030* | |||
Paleogene | Oligocene | 33.9* | ||
Eocene | 56.0* | |||
Paleocene | 66.0* | |||
Mesozoic | Cretaceous | Late Cretaceous | 100.5* | |
Early Cretaceous | c. 145.0 | |||
Jurassic | Late Jurassic | 163.5 ± 1.0 | ||
Middle Jurassic | 174.1 ± 1.0* | |||
Early Jurassic | 201.3 ± 0.2* | |||
Triassic | Late Triassic | c. 235* | ||
Middle Triassic | 247.2 | |||
Early Triassic | 252.2 ± 0.5* | |||
Paleozoic | Permian | 298.9 ± 0.2* | ||
Carboniferous | Pennsylvanian | 323.2 ± 0.4* | ||
Mississippian | 358.9 ± 0.4* | |||
Devonian | 419.2 ± 3.2* | |||
Silurian | 443.4 ± 1.5* | |||
Ordovician | 485.4 ± 1.9* | |||
Cambrian | 541.0 ± 1.0* | |||
Proterozoic | Neoproterozoic | Ediacaran | Precambrian | c. 635* |
Cryogenian | 850 | |||
Tonian | 1000 | |||
Mesoproterozoic | Stenian | 1200 | ||
Ectasian | 1400 | |||
Calymmian | 1600 | |||
Paleoproterozoic | Statherian | 1800 | ||
Orosirian | 2050 | |||
Rhyacian | 2300 | |||
Siderian | 2500 | |||
Archean | Neoarchean | 2800 | ||
Mesoarchean | 3200 | |||
Paleoarchean | 3600 | |||
Eoarchean | 4000 | |||
Hadean | 4567 |
Notes
- ^ ISBN 978-1-119-22834-9.
- ISBN 978-1-119-22834-9.
- ISBN 978-1-119-22834-9.
- ISBN 978-1-119-22834-9.
- ^ "Geological Time | Digital Atlas of Ancient Life". Retrieved 2021-04-18.
- ISBN 978-1-119-22834-9.
- ^ Hutton, James (1788). "Theory of the Earth; or an Investigation of the Laws Observable in the Composition, Dissolution, and Restoration of Land upon the Globe." Transactions of the Royal Society of Edinburgh. Royal Society of Edinburgh. 1 (Part 2): 209–304.
- ^ "Geological Time | Digital Atlas of Ancient Life". Retrieved 2021-04-25.
- ISSN 0016-7606.
- ^ "7.1: Relative Dating". Geosciences LibreTexts. 2019-11-04. Retrieved 2021-04-23.
- ^ "7.2: Absolute Dating". Geosciences LibreTexts. 2019-11-04. Retrieved 2021-04-23.
- ISBN 978-1-119-22834-9.
External links
- Geology – Earth history | Encyclopedia Britannica
- Historical Geology | OpenGeology.org
- GEOL 102 Historical Geology | Lecture notes for course at the University of Maryland