Seismology is the scientific study of earthquakes and the generation and propagation of elastic waves through the Earth or other planetary bodies. It also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, glacial, fluvial, oceanic microseism, atmospheric, and artificial processes such as explosions and human activities. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of Earth motion as a function of time, created by a seismograph is called a seismogram. A seismologist is a scientist works in basic or applied seismology.
An iceberg is a piece of freshwater ice more than 15 m long that has broken off a glacier or an ice shelf and is floating freely in open water. Smaller chunks of floating glacially derived ice are called "growlers" or "bergy bits". Much of an iceberg is below the water's surface, which led to the expression "tip of the iceberg" to illustrate a small part of a larger unseen issue. Icebergs are considered a serious maritime hazard.
An ice shelf is a large platform of glacial ice floating on the ocean, fed by one or multiple tributary glaciers. Ice shelves form along coastlines where the ice thickness is insufficient to displace the more dense surrounding ocean water. The boundary between the ice shelf (floating) and grounded ice is referred to as the grounding line; the boundary between the ice shelf and the open ocean is the ice front or calving front.
Post-glacial rebound is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound and isostatic depression are phases of glacial isostasy, the deformation of the Earth's crust in response to changes in ice mass distribution. The direct raising effects of post-glacial rebound are readily apparent in parts of Northern Eurasia, Northern America, Patagonia, and Antarctica. However, through the processes of ocean siphoning and continental levering, the effects of post-glacial rebound on sea level are felt globally far from the locations of current and former ice sheets.
An ice stream is a region of fast-moving ice within an ice sheet. It is a type of glacier, a body of ice that moves under its own weight. They can move upwards of 1,000 metres (3,300 ft) a year, and can be up to 50 kilometres (31 mi) in width, and hundreds of kilometers in length. They tend to be about 2 km (1.2 mi) deep at the thickest, and constitute the majority of the ice that leaves the sheet. In Antarctica, the ice streams account for approximately 90% of the sheet's mass loss per year, and approximately 50% of the mass loss in Greenland.
Jakobshavn Glacier, also known as Ilulissat Glacier, is a large outlet glacier in West Greenland. It is located near the Greenlandic town of Ilulissat and ends at the sea in the Ilulissat Icefjord.
The geology of Iceland is unique and of particular interest to geologists. Iceland lies on the divergent boundary between the Eurasian plate and the North American plate. It also lies above a hotspot, the Iceland plume. The plume is believed to have caused the formation of Iceland itself, the island first appearing over the ocean surface about 16 to 18 million years ago. The result is an island characterized by repeated volcanism and geothermal phenomena such as geysers.
A cryoseism, ice quake or frost quake, is a seismic event caused by a sudden cracking action in frozen soil or rock saturated with water or ice, or by stresses generated at frozen lakes. As water drains into the ground, it may eventually freeze and expand under colder temperatures, putting stress on its surroundings. This stress builds up until relieved explosively in the form of a cryoseism. The requirements for a cryoseism to occur are numerous; therefore, accurate predictions are not entirely possible and may constitute a factor in structural design and engineering when constructing in an area historically known for such events. Speculation has been made between global warming and the frequency of cryoseisms.
The Gamburtsev Mountain Range is a subglacial mountain range located in East Antarctica, just underneath the lofty Dome A, near the Southern Pole of Inaccessibility. The range was discovered by the 3rd Soviet Antarctic Expedition in 1958 and is named for Soviet geophysicist Grigoriy A. Gamburtsev. It is approximately 1,200 kilometres (750 mi) long, and the mountains are believed to be about 2,700 metres (8,900 ft) high, although they are completely covered by over 600 metres (2,000 ft) of ice and snow. The Gamburtsev Mountain Range is about the same size as the European Alps. As of 2008, it was unknown how the mountains were formed due to the lack of data. Studies conducted during the International Polar year demonstrated that ancient plate collisions produced a core that was rejuvenated in the early to mid-Mesozoic. The main features of the range formed before 34 million years ago, when the area was covered by the present ice sheet. Current models suggest that the East Antarctic ice sheet was formed from the glaciers that began sliding down the Gamburtsev range at the end of the Eocene. Vostok Subglacial Highlands form an east extension of Gamburtsev Subglacial Mountains.
The receiver function technique is a way to image the structure of the Earth and its internal boundaries by using the information from teleseismic earthquakes recorded at a three-component seismograph.
Ice calving, also known as glacier calving or iceberg calving, is the breaking of ice chunks from the edge of a glacier. It is a form of ice ablation or ice disruption. It is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse. The ice that breaks away can be classified as an iceberg, but may also be a growler, bergy bit, or a crevasse wall breakaway.
Lunar seismology is the study of ground motions of the Moon and the events, typically impacts or moonquakes, that excite them.
A series of small volcanic earthquakes measuring less than 4.0 on the Richter magnitude scale took place in the sparsely populated Nazko area of the Central Interior of British Columbia, Canada, from October 9, 2007, to June 12, 2008. They occurred just west of Nazko Cone, a small tree-covered cinder cone that last erupted about 7,200 years ago.
In seismology, doublet earthquakes – and more generally, multiplet earthquakes – were originally identified as multiple earthquakes with nearly identical waveforms originating from the same location. They are now characterized as distinct earthquake sequences having two main shocks of similar magnitude, sometimes occurring within tens of seconds, but sometimes separated by years. The similarity of magnitude – often within 0.4 magnitude – distinguishes multiplet events from aftershocks, which start at about 1.2 magnitude less than the parent shock and decrease in magnitude and frequency according to known laws.
Deglaciation is the transition from full glacial conditions during ice ages, to warm interglacials, characterized by global warming and sea level rise due to change in continental ice volume. Thus, it refers to the retreat of a glacier, an ice sheet or frozen surface layer, and the resulting exposure of the Earth's surface. The decline of the cryosphere due to ablation can occur on any scale from global to localized to a particular glacier. After the Last Glacial Maximum, the last deglaciation begun, which lasted until the early Holocene. Around much of Earth, deglaciation during the last 100 years has been accelerating as a result of climate change, partly brought on by anthropogenic changes to greenhouse gases.
The Bransfield Basin is a back-arc rift basin located off the northern tip of the Antarctic Peninsula. The basin lies within a Northeast and Southwest trending strait that separates the peninsula from the nearby South Shetland Islands to the Northwest. The basin extends for more than 500 kilometres from Smith Island to a portion of the Hero Fracture Zone. The basin can be subdivided into three basins: Western, Central, and Eastern. The Western basin is 130 kilometres long by 70 kilometres wide with a depth of 1.3 kilometres, the Central basin is 230 kilometres long by 60 kilometres wide with a depth of 1.9 kilometres, and the Eastern basin is 150 kilometres long by 40 kilometres wide with a depth of over 2.7 kilometres. The three basins are separated by the Deception Island and Bridgeman Island. The moho depth in the region has been seismically interpreted to be roughly 34 kilometres deep.
Marine geophysics is the scientific discipline that employs methods of geophysics to study the world's ocean basins and continental margins, particularly the solid earth beneath the ocean. It shares objectives with marine geology, which uses sedimentological, paleontological, and geochemical methods. Marine geophysical data analyses led to the theories of seafloor spreading and plate tectonics.
In the afternoon of Wednesday 25 March 1998, a very large magnitude 8.1 earthquake struck a remote area of the Southern Ocean. Its epicentre was located roughly 450 km (280 mi) north of George V Land and roughly 700 km (435 mi) northwest of the Balleny Islands in Antarctica. Due to the remote location of the earthquake, there were no reports of anyone feeling any shaking or any damage being caused. The event was a complex intraplate earthquake within the Antarctic Plate. To date it is the largest recorded earthquake in Antarctica, and is the largest recorded earthquake to have been caused by post-glacial rebound. The earthquake occurred in an area which previously had very little seismic activity, and so such a large event was unprecedented in the seismic record.
Fluvial seismology is the application of seismological methods to understand river processes, such as discharge, erosion, and streambed evolution. Flowing water and the movement of sediments along the streambed generate elastic (seismic) waves that propagate into the surrounding Earth materials. Seismometers can record these signals, which can be analyzed to illuminate different fluvial processes such as turbulent water flow and bedload transport. Seismic methods have been used to observe discharge values that range from single-digits up through tens of thousands of cubic feet per second (cfs).
Ruth Mottram is a British climate scientist who is a researcher at the Danish Meteorological Institute. Her research considers the development of climate models and the dynamics of glaciers and ice sheets in the climate system.
