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The Paleogene Period is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 Ma to the beginning of the Neogene Period 23.03 Ma. It is the first period of the Cenozoic Era and is divided into the Paleocene, Eocene, and Oligocene epochs. The earlier term Tertiary Period was used to define the time now covered by the Paleogene Period and subsequent Neogene Period; despite no longer being recognized as a formal stratigraphic term, "Tertiary" still sometimes remains in informal use. Paleogene is often abbreviated "Pg", although the United States Geological Survey uses the abbreviation "Pe" for the Paleogene on the Survey's geologic maps.
Plate tectonics is the scientific theory that Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century. Plate tectonics came to be accepted by geoscientists after seafloor spreading was validated in the mid-to-late 1960s.
Seafloor spreading, or seafloor spread, is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.
A lithosphere is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time scales of up to thousands of years or more. The crust and upper mantle are distinguished on the basis of chemistry and mineralogy.
Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second plate, the heavier plate dives beneath the other and sinks into the mantle. A region where this process occurs is known as a subduction zone, and its surface expression is known as an arc-trench complex. The process of subduction has created most of the Earth's continental crust. Rates of subduction are typically measured in centimeters per year, with rates of convergence as high as 11 cm/year.
A convergent boundary is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, orogenesis, destruction of lithosphere, and deformation. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types.
The Sunda Arc is a volcanic arc that produced the volcanoes that form the topographic spine of the islands of Sumatra, Nusa Tenggara, Java, the Sunda Strait, and the Lesser Sunda Islands. The Sunda Arc begins at Sumatra and ends at Flores, and is adjacent to the Banda Arc. The Sunda Arc is formed via the subduction of the Indo-Australian Plate beneath the Sunda and Burma plates at a velocity of 63–70 mm/year.
Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthquakes are the planet's most powerful, with moment magnitudes (Mw) that can exceed 9.0. Since 1900, all earthquakes of magnitude 9.0 or greater have been megathrust earthquakes.
A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about 2,600 meters (8,500 ft) and rises about 2,000 meters (6,600 ft) above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin.
Episodic tremor and slip (ETS) is a seismological phenomenon observed in some subduction zones that is characterized by non-earthquake seismic rumbling, or tremor, and slow slip along the plate interface. Slow slip events are distinguished from earthquakes by their propagation speed and focus. In slow slip events, there is an apparent reversal of crustal motion, although the fault motion remains consistent with the direction of subduction. ETS events themselves are imperceptible to human beings and do not cause damage.
Partial melting is the phenomenon that occurs when a rock is subjected to temperatures high enough to cause certain minerals to melt, but not all of them. Partial melting is an important part of the formation of all igneous rocks and some metamorphic rocks, as evidenced by a multitude of geochemical, geophysical and petrological studies.
Susan Y. Schwartz is a scientist at the University of California, Santa Cruz known for her research on earthquakes, through field projects conducted in locations in Costa Rica and the San Andreas Fault.
In geology, the slab is a significant constituent of subduction zones.
Crustal recycling is a tectonic process by which surface material from the lithosphere is recycled into the mantle by subduction erosion or delamination. The subducting slabs carry volatile compounds and water into the mantle, as well as crustal material with an isotopic signature different from that of primitive mantle. Identification of this crustal signature in mantle-derived rocks is proof of crustal recycling.
The Hikurangi Margin is New Zealand's largest subduction zone and fault.
Flat slab subduction is characterized by a low subduction angle beyond the seismogenic layer and a resumption of normal subduction far from the trench. A slab refers to the subducting lower plate. A broader definition of flat slab subduction includes any shallowly dipping lower plate, as in western Mexico. Flat slab subduction is associated with the pinching out of the asthenosphere, an inland migration of arc magmatism, and an eventual cessation of arc magmatism. The coupling of the flat slab to the upper plate is thought to change the style of deformation occurring on the upper plate's surface and form basement-cored uplifts like the Rocky Mountains. The flat slab also may hydrate the lower continental lithosphere and be involved in the formation of economically important ore deposits. During the subduction, a flat slab itself may deform or buckle, causing sedimentary hiatus in marine sediments on the slab. The failure of a flat slab is associated with ignimbritic volcanism and the reverse migration of arc volcanism. Multiple working hypotheses about the cause of flat slabs are subduction of thick, buoyant oceanic crust (15–20 km) and trench rollback accompanying a rapidly overriding upper plate and enhanced trench suction. The west coast of South America has two of the largest flat slab subduction zones. Flat slab subduction is occurring at 10% of subduction zones.
Earth's crustal evolution involves the formation, destruction and renewal of the rocky outer shell at that planet's surface.
Laura Martin Wallace is a geodetic principal scientist who works between the University of Texas at Austin and GNS Science in New Zealand. She was elected Fellow of the Royal Society Te Apārangi in 2018.
Karen Fischer is an American seismologist known for her research on the structure of Earth's mantle, its lithosphere, and how subduction zones change over geologic history.
Suzanne Carbotte is a marine geophysicist known for her research on the formation of new oceanic crust.
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- ↑ Wallace, L. M.; Webb, S. C.; Ito, Y.; Mochizuki, K.; Hino, R.; Henrys, S.; Schwartz, S. Y.; Sheehan, A. F. (2016-05-06). "Slow slip near the trench at the Hikurangi subduction zone, New Zealand". Science. 352 (6286): 701–704. Bibcode:2016Sci...352..701W. doi: 10.1126/science.aaf2349 . ISSN 0036-8075. PMID 27151867. S2CID 206647253.
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- ↑ McGarr, A.; Bekins, B.; Burkardt, N.; Dewey, J.; Earle, P.; Ellsworth, W.; Ge, S.; Hickman, S.; Holland, A.; Majer, E.; Rubinstein, J.; Sheehan, Anne F. (2015-02-20). "Coping with earthquakes induced by fluid injection". Science. 347 (6224): 830–831. Bibcode:2015Sci...347..830M. doi:10.1126/science.aaa0494. ISSN 0036-8075. PMID 25700505. S2CID 206632570.
- ↑ Palmer, Jane (2011). "Eavesdropping on Tsunamis: Underwater instruments assist early-warning systems". Spheres (6): 7. ISSN 2380-2855. JSTOR 24352818.
- ↑ "How commercial vessels could become tsunami early-warning systems". CU Boulder Today. 2020-12-10. Retrieved 2021-07-25.
- ↑ Hossen, M. J.; Mulia, Iyan E.; Mencin, David; Sheehan, Anne F. (2021). "Data Assimilation for Tsunami Forecast With Ship-Borne GNSS Data in the Cascadia Subduction Zone". Earth and Space Science. 8 (3): e2020EA001390. Bibcode:2021E&SS....801390H. doi: 10.1029/2020EA001390 . ISSN 2333-5084.
- ↑ Wallace, L. M.; Webb, S. C.; Ito, Y.; Mochizuki, K.; Hino, R.; Henrys, S.; Schwartz, S. Y.; Sheehan, A. F. (6 May 2016). "Slow slip near the trench at the Hikurangi subduction zone, New Zealand". Science. 352 (6286): 701–704. Bibcode:2016Sci...352..701W. doi: 10.1126/science.aaf2349 . PMID 27151867. S2CID 206647253.
- ↑ Warren-Smith, E.; Fry, B.; Wallace, L.; Chon, E.; Henrys, S.; Sheehan, A.; Mochizuki, K.; Schwartz, S.; Webb, S.; Lebedev, S. (June 2019). "Episodic stress and fluid pressure cycling in subducting oceanic crust during slow slip". Nature Geoscience. 12 (6): 475–481. Bibcode:2019NatGe..12..475W. doi:10.1038/s41561-019-0367-x. ISSN 1752-0908. S2CID 182644542.
- ↑ "New Zealand Geophysics Prize » Geoscience Society of New Zealand". Geoscience Society of New Zealand. Retrieved 30 July 2021.
