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102-399: Initiation of volcanism at Coso preceded the onset of Basin and Range crustal extension there, as expressed by normal faulting. The earlier of the two principal periods of volcanism began with the emplacement of basalt flows over a surface of little relief. Then, during the ensuing period of approximately 1.5 million years, eruptive activity included chemically more evolved rocks erupted upon

204-787: A mid-ocean ridge , such as the Mid-Atlantic Ridge , has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from

306-493: A common feature at explosive volcanoes on Earth. Pyroclastic flows have been found on Venus, for example at the Dione Regio volcanoes. A phreatic eruption can occur when hot water under pressure is depressurised. Depressurisation reduces the boiling point of the water, so when depressurised the water suddenly boils. Or it may happen when groundwater is suddenly heated, flashing to steam suddenly. When water turns into steam in

408-399: A faulted terrain of substantial relief. Following a 1.5-million-year hiatus with few eruptions, a bimodal volcanic field of basalt lava flows and rhyolite lava domes and flows developed on Basin and Range terrain of essentially the same form as today's landscape. Many of the young basalt flows are inter-canyon, occupying parts of the present-day drainage system. The Coso Volcanic Field

510-606: A foreshock. All three earthquakes have been described by the United States Geological Survey as occurring via shallow strike-slip mechanisms. Subsequent seismic activity occurred along two intersecting faults in the Little Lake Fault Zone. A significant series of additional earthquakes followed the foreshock, with the majority of magnitudes ranging approximately 2–4 M w  . By the evening of July 5, more than 1,400 earthquakes occurred,

612-657: A greater magnitude, was felt more strongly, with an intensity of 4.5 in some places, and 3.9 downtown. According to the City of Los Angeles's Twitter account, the threshold will be lowered after this event. The broad context of the Ridgecrest earthquakes is the Eastern California Shear Zone (ECSZ), a seismically active region east of the southern segment of the San Andreas Fault (SAF) and largely coincident with

714-425: A lava flow to cool rapidly. This splinters the surface of the lava, and the magma then collects into sacks that often pile up in front of the flow, forming a structure called a pillow. A’a lava has a rough, spiny surface made of clasts of lava called clinkers. Block lava is another type of lava, with less jagged fragments than in a’a lava. Pahoehoe lava is by far the most common lava type, both on Earth and probably

816-409: A mechanical standpoint it is a water filled crevasse turned upside down. As magma rises into the vertical crack, the low density of the magma compared to the wall rock means that the pressure falls less rapidly than in the surrounding denser rock. If the average pressure of the magma and the surrounding rock are equal, the pressure in the dike exceeds that of the enclosing rock at the top of the dike, and

918-564: A million years), any traces of it have long since vanished. There are small traces of unstable isotopes in common minerals, and all the terrestrial planets , and the Moon, experience some of this heating. The icy bodies of the outer solar system experience much less of this heat because they tend to not be very dense and not have much silicate material (radioactive elements concentrate in silicates). On Neptune's moon Triton , and possibly on Mars, cryogeyser activity takes place. The source of heat

1020-537: A moon of Saturn . The ejecta may be composed of water, liquid nitrogen , ammonia , dust, or methane compounds. Cassini–Huygens also found evidence of a methane-spewing cryovolcano on the Saturnian moon Titan , which is believed to be a significant source of the methane found in its atmosphere. It is theorized that cryovolcanism may also be present on the Kuiper Belt Object Quaoar . A 2010 study of

1122-580: A new transform fault that will replace the San Andreas Fault. Along the eastern front of the Sierra Nevada strike-slip faulting happens on the Owens Valley Fault (OVF), part of which ruptured in the 1872 Owens Valley earthquake near Lone Pine. The OVF runs south, largely along U.S. Highway 395, through Bishop , Big Pine , Independence , and Lone Pine to the northern end of Rose Valley and

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1224-455: A partially molten core. However, the Moon does have many volcanic features such as maria (the darker patches seen on the Moon), rilles and domes . The planet Venus has a surface that is 90% basalt , indicating that volcanism played a major role in shaping its surface. The planet may have had a major global resurfacing event about 500 million years ago, from what scientists can tell from

1326-480: A phreatic eruption, it expands at supersonic speeds, up to 1,700 times its original volume. This can be enough to shatter solid rock, and hurl rock fragments hundreds of metres. A phreatomagmatic eruption occurs when hot magma makes contact with water, creating an explosion. One mechanism for explosive cryovolcanism is cryomagma making contact with clathrate hydrates . Clathrate hydrates, if exposed to warm temperatures, readily decompose. A 1982 article pointed out

1428-535: A potential resource of 650 megawatts electric with a nominal life span of 30 years. Judged by the youthfulness of the rhyolite lavas and by a zone of low seismic velocity crust roughly beneath the rhyolite, a magma body may be the source of thermal energy for the geothermal system. Commercial power development began in the 1980s. Located within the Naval Air Weapons Station China Lake Station near Ridgecrest, California , power plants at

1530-494: A rigid open channel, in the lithosphere and settles at the level of hydrostatic equilibrium . Despite how it explains observations well (which newer models cannot), such as an apparent concordance of the elevation of volcanoes near each other, it cannot be correct and is now discredited, because the lithosphere thickness derived from it is too large for the assumption of a rigid open channel to hold. Unlike silicate volcanism, where melt can rise by its own buoyancy until it reaches

1632-631: A significant amount of the right-slip motion of the ECSZ, and (along with the Airport Lake fault zone) may be a major tectonic boundary. South of Little Lake the SNFF continues south along the west side of Indian Wells Valley (where Ridgecrest is situated), then curves west (roughly along California Highway 14) before connecting with the Garlock Fault. The easterly striking left-slip Garlock Fault south of Ridgecrest

1734-446: A uniform subsurface ocean, may instead take place from discrete liquid reservoirs. The first way these can form is a plume of warm ice welling up and then sinking back down, forming a convection current. A model developed to investigate the effects of this on Europa found that energy from tidal heating became focused in these plumes, allowing melting to occur in these shallow depths as the plume spreads laterally (horizontally). The next

1836-407: A year. The Ridgecrest earthquake sequence of 1995 was particularly notable, having eight events M ≥ 4.0. This sequence was similar to the 2019 earthquakes in having two main shocks: an M L  5.4 earthquake on August 17 located 11 miles north of Ridgecrest, and an M L  5.8 earthquake on September 20, located about a mile south-southwest of the first earthquake. Another shock on the 24th

1938-456: A zone of faulting extending into Nevada and northward, where the Sierra Nevada (Sierran) microplate that underlies most of Central California is being torn away from North American continent. Currently approximately one-quarter of the slippage between the Pacific plate and North America is accommodated through the ECSZ and Walker Lane; it is expected that eventually the shearing will consolidate into

2040-592: Is a switch from vertical to horizontal propagation of a fluid filled crack. Another mechanism is heating of ice from release of stress through lateral motion of fractures in the ice shell penetrating it from the surface, and even heating from large impacts can create such reservoirs. When material of a planetary body begins to melt, the melting first occurs in small pockets in certain high energy locations, for example grain boundary intersections and where different crystals react to form eutectic liquid , that initially remain isolated from one another, trapped inside rock. If

2142-463: Is best known for its Pleistocene rhyolite. Thirty-eight rhyolite domes and flows form an elongate array atop a north-trending 8 by 20 kilometres (5.0 mi × 12.4 mi) horst of Mesozoic bedrock. Nearby uneroded constructional forms are exhibited by most domes. Many are nested within tuff ring craters, and a few filled and overrode their craters to feed flows a kilometer or two long. The two oldest domes contain several percent phenocrysts ;

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2244-415: Is common in volcanic areas, such as Long Valley Caldera near Mammoth Lakes , and Yellowstone Caldera at Yellowstone . The Coso Volcanic Field shows examples of volcanic activity, probably last active 30,000 to 40,000 years ago, but ash emission and small cone building episodes may be Holocene (>10,000 years) in age. Volcanism Volcanism , vulcanism , volcanicity , or volcanic activity

2346-447: Is driven by exsolution of volatiles that were previously dissolved into the cryomagma, similar to what happens in explosive silicate volcanism as seen on Earth, which is what is mainly covered below. Silica-rich magmas cool beneath the surface before they erupt. As they do this, bubbles exsolve from the magma. As the magma nears the surface, the bubbles and thus the magma increase in volume. The resulting pressure eventually breaks through

2448-598: Is entirely in the form of water, which freezes into ice on the frigid surface. This process is known as cryovolcanism , and is apparently most common on the moons of the outer planets of the Solar System . In 1989, the Voyager 2 spacecraft observed cryovolcanoes (ice volcanoes) on Triton , a moon of Neptune , and in 2005 the Cassini–Huygens probe photographed fountains of frozen particles erupting from Enceladus ,

2550-462: Is external (heat from the Sun) rather than internal. Decompression melting happens when solid material from deep beneath the body rises upwards. Pressure decreases as the material rises upwards, and so does the melting point. So, a rock that is solid at a given pressure and temperature can become liquid if the pressure, and thus melting point, decreases even if the temperature stays constant. However, in

2652-477: Is formed when fluids and gases under pressure erupt to the surface, bringing mud with them. This pressure can be caused by the weight of overlying sediments over the fluid which pushes down on the fluid, preventing it from escaping, by fluid being trapped in the sediment, migrating from deeper sediment into other sediment or being made from chemical reactions in the sediment. They often erupt quietly, but sometimes they erupt flammable gases like methane. Cryovolcanism

2754-503: Is much more than the ambient pressure. Not only that, but any volatiles in the water will exsolve. The combination of these processes will release droplets and vapor, which can rise up the fracture, creating a plume. This is thought to be partially responsible for Enceladus's ice plumes. On Earth, volcanoes are most often found where tectonic plates are diverging or converging , and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example,

2856-535: Is one of California's longest active faults, and marks the boundary between different styles of tectonic deformation. It has been called "somewhat enigmatic" in that it appears to neither offset, nor be offset by, any of the active, NW trending strike-slip faults that cross the ECSZ. In particular, even though the Little Lake Fault is in general alignment with the Blackwater Fault (and its southern extension,

2958-487: Is partially due to the fact that melted material tends to be more mobile and less dense than the materials from which they were produced, which can cause it to rise to the surface. There are multiple ways to generate the heat needed for volcanism. Volcanism on outer solar system moons is powered mainly by tidal heating . Tidal heating caused by the deformation of a body's shape due to mutual gravitational attraction, which generates heat. Earth experiences tidal heating from

3060-460: Is pressurised in the same way. For a crack in the ice shell to propagate upwards, the fluid in it must have positive buoyancy or external stresses must be strong enough to break through the ice. External stresses could include those from tides or from overpressure due to freezing as explained above. There is yet another possible mechanism for ascent of cryovolcanic melts. If a fracture with water in it reaches an ocean or subsurface fluid reservoir,

3162-461: Is the eruption of volatiles into an environment below their freezing point. The processes behind it are different to silicate volcanism because the cryomagma (which is usually water-based) is normally denser than its surroundings, meaning it cannot rise by its own buoyancy. Sulfur lavas have a different behaviour to silicate ones. First, sulfur has a low melting point of about 120 degrees Celsius. Also, after cooling down to about 175 degrees Celsius

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3264-461: Is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. It is caused by the presence of a heat source, usually internally generated, inside the body; the heat is generated by various processes, such as radioactive decay or tidal heating . This heat partially melts solid material in the body or turns material into gas. The mobilized material rises through

3366-520: Is transferred through or around the Garlock Fault, remains unanswered. Geodetic measurements show that the slip-rate of Garlock Fault is currently less than half of its estimated long-term geological rate. This may indicate that the Garlock Fault is in the late stages of its earthquake cycle. The Scodie Lineament is a zone of microseismicity extending southwest (paralleling the Garlock Fault) from near Walker Pass (due west of Ridgecrest) to align with

3468-621: The Los Angeles Aqueduct , were conducted across the Los Angeles metropolitan area . The Ventura County Fire Department dispatched personnel to survey the county for damage. Naval Air Weapons Station China Lake brought in additional personnel to conduct damage assessments. The USGS sent geologists to Kern County soon after the foreshock to look for a surface rupture and collect data. Disneyland suspended ride operations for inspection. On July 4, seismologist Dr. Lucy Jones said there

3570-527: The Modified Mercalli Intensity Scale , what is considered "light shaking" with only slight damage (such as cracked plaster). The intensity expected for Thursday's quake (on the 4th) was calculated to be less than that, so no alert was issued. While the actual shaking reached intensity 4 in some areas in the northern part of the county, in other parts the intensity reached only a level 2 or 3, not noticed by many people. The second quake, having

3672-731: The Mojave Desert , featuring multiple right-lateral strike-slip faults paralleling the SAF. It is transected by the Garlock Fault , extending northeast and then east from the SAF's "Big Bend" to the Death Valley Fault near the Nevada state line, passing Ridgecrest about fifteen miles to the south. The ECSZ extends north along the east front of the Sierra Nevada Mountains to Walker Lane ,

3774-457: The Moon , deforming by up to 1 metre (3 feet), but this does not make up a major portion of Earth's total heat . During a planet's formation , it would have experienced heating from impacts from planetesimals , which would have dwarfed even the asteroid impact that caused the extinction of dinosaurs . This heating could trigger differentiation , further heating the planet. The larger a body is,

3876-436: The contact angle of the melted material allows the melt to wet crystal faces and run along grain boundaries , the melted material will accumulate into larger quantities. On the other hand, if the angle is greater than about 60 degrees, much more melt must form before it can separate from its parental rock. Studies of rocks on Earth suggest that melt in hot rocks quickly collects into pockets and veins that are much larger than

3978-626: The core–mantle boundary , 3,000 kilometers (1,900 mi) deep within Earth. This results in hotspot volcanism , of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another. In 1912–1952, in the Northern Hemisphere, studies show that within this time, winters were warmer due to no massive eruptions that had taken place. These studies demonstrate how these eruptions can cause changes within

4080-465: The exoplanet COROT-7b , which was detected by transit in 2009, suggested that tidal heating from the host star very close to the planet and neighboring planets could generate intense volcanic activity similar to that found on Io. 2019 Ridgecrest earthquakes The 2019 Ridgecrest earthquakes (more commonly referred to in scientific literature as the 2019 Ridgecrest earthquake sequence ) of July 4 and 5 occurred north and northeast of

4182-405: The grain size, in contrast to the model of rigid melt percolation . Melt, instead of uniformly flowing out of source rock, flows out through rivulets which join to create larger veins. Under the influence of buoyancy , the melt rises. Diapirs may also form in non-silicate bodies, playing a similar role in moving warm material towards the surface. A dike is a vertical fluid-filled crack, from

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4284-510: The 7.1  M w   mainshock. Structural damage and two building fires—one of which destroyed half of a home—occurred in Ridgecrest. One mobile home was knocked off its foundation and deemed uninhabitable. Around 20 injuries were reported, primarily from shattered glass and falling debris. Some gas lines broke, prompting utility companies to shut off service. Businesses experienced product loss, with goods falling off shelves. Emergency personnel responded to nearly two dozen incidents in

4386-462: The 7.1 M w   event, with the total number of aftershocks exceeding 3,000 by the morning of July 7. Geologists at the USGS estimate an additional 34,000 aftershocks in the six months following the earthquakes. On June 3, 2020, at 6:32 PM PST, a 5.5 M w   aftershock was recorded 11 miles south of Searles Valley. This aftershock is tied for the strongest aftershock following

4488-580: The Calico Fault), and a connection is "strongly suspected", and though the aftershocks triggered along the entire length of these faults by the 1992 Landers earthquake suggests a structural continuity, yet the surficial geology shows that "the Blackwater fault ends a few kilometers short of the Garlock fault." How to explain this apparent lack of fault offsetting, and the larger question of how strain (dislocation)

4590-536: The City of Ridgecrest, but due to the dip of the fault the epicenters of the 2019 earthquakes are mainly under the NWC, where the Little Lake Fault intersects the broad north–south oriented Airport Lake Fault Zone. The fault continues on to the Garlock Fault about 15 miles southeast of Ridgecrest, just past Searles Station. East of Rose Valley, between the nearly parallel ends of the Owens Valley and Little Lake faults, lies

4692-510: The Coso Geothermal were operated by Caithness Energy , LLC (Reno, Nevada) and sold in 2006. It currently produces 270 MW from four geothermal power plants. More than 100 wells have been drilled throughout the field, with production depths from 2,000 to 12,000 feet (610 to 3,700 m), and temperatures from 200 to 350 °C (392 to 662 °F). Coso began generating electricity in 1987. Improvements have resulted in more efficient use of

4794-653: The Coso Range and Coso Volcanic Field (a notable geothermal field). These lie in a zone where stress and strike-slip movement from the OVF is transferred to various other faults to the south and east, including the Little Lake and Airport Lake faults. The Little Lake Fault has been considered a splay (branch) of the Sierra Nevada (or Sierran) Frontal Fault (SNFF) (formed by the uplift of the Sierra Nevada), but may actually accommodate

4896-470: The Coso Volcanic Fields was heavily exploited by Native American Coso People to make knives, projectile points, and the like (Hughes 1998). The chief period of exploitation was between approximately 3000 and 1000 years ago, when people mined obsidian by constructing benches in hillsides and digging deep pits to access raw materials (Elston and Zeier 1984; Gilreath and Hildebrand 1997). Obsidian from

4998-460: The Earth's atmosphere. Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere . Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines. Earth's Moon has no large volcanoes and no current volcanic activity, although recent evidence suggests it may still possess

5100-554: The European Mars Express spacecraft has found evidence that volcanic activity may have occurred on Mars in the recent past as well. Jupiter 's moon Io is the most volcanically active object in the Solar System because of tidal interaction with Jupiter. It is covered with volcanoes that erupt sulfur , sulfur dioxide and silicate rock, and as a result, Io is constantly being resurfaced. There are only two planets in

5202-569: The Little Lake Fault Zone. Relatively minor damage resulted from the initial foreshock, though some building fires were reported in Ridgecrest near the epicenter . The main quake on July 5 cut power to at least 3,000 residents in Ridgecrest. Effects were felt across much of Southern California , parts of Arizona and Nevada , as far north as the San Francisco Bay Area and Sacramento , and as far south as Baja California , Mexico. An estimated 20 million people experienced

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5304-1089: The Little Lake Fault and into Owens Valley. Smaller earthquakes are quite common. In the Ridgecrest area these include a M L 5.2 earthquake in October 1961 near Brown (approximately halfway between Ridgecrest and Little Lake) that was felt in Independence and Los Angeles; it was preceded by eight minutes by an M L  3.4 foreshock felt in China Lake (east of Ridgecrest). Additional earthquakes struck near Walker Pass in 1961 (M L  5.3), 1962 (M L  4.9), and 1979 (M L  4.3). In 1977 two small quakes that hit Ridgecrest in February were followed by another pair of small earthquakes in March. Seismicity in Indian Wells Valley has been characterized by swarms of thousands of earthquakes, some lasting for more than

5406-529: The M w   6.4 foreshock, California Governor Gavin Newsom approved an emergency proclamation for Kern County . Local emergency responders such as the Los Angeles Police Department used social media to alert the public that they were aware of the earthquake and to only use 9-1-1 if there was dangerous conditions or injuries. Routine protocol inspections of major infrastructure, including

5508-519: The Ridgecrest earthquakes, which many people assumed to be a failure. This app, developed by the City of Los Angeles in partnership with the USGS, and released at the beginning of 2019, is intended to give users located in Los Angeles County some tens of seconds of warning of possibly damaging shaking from a non-local earthquake. ShakeAlertLA is triggered by the ShakeAlert system being developed by

5610-566: The Sierra Nevada, due west from Ridgecest), with aftershocks continuing for nearly a year. The 1952 Kern County earthquake ( M s 7.5, M w  7.3 ), considered the biggest earthquake to hit California since the 1906 San Francisco earthquake , occurred on the White Wolf fault south of Bakersfield, and likely connected with the Walker Pass earthquake via the Scodie Lineament. At

5712-456: The Sugarloaf and West Sugarloaf were the most commonly exploited geochemical types (Eerkens and Rosenthal 2004; Ericson and Glascock 2004). The Coso Volcanic Field is well known as a geothermal area. Fumaroles are present along faults bounding the rhyolite-capped horst and locally within the rhyolite field. A multi-disciplinary program of geothermal assessment carried out in the 1970s defined

5814-421: The USGS that monitors earthquakes across Southern California. When that system detects an earthquake of magnitude 5.0 or greater it calculates the intensity of shaking to be expected in Los Angeles County, factoring in the calculated magnitude and distance of the source. At the time of the Ridgecrest earthquakes the threshold for issuing an alert was an expected shaking intensity in Los Angeles County of 4 (IV) on

5916-589: The White Wolf Fault, scene of the 1952 Kern County earthquake south of Bakersfield. The nature of the seismicity suggests an early stage in the formation of a strike-slip fault, before localized faulting in the shear zone has connected to form a continuous structure. A large portion of the slippage between the Pacific and North American plates is accommodated in the Eastern California Shear Zone (ECSZ), resulting in many large earthquakes even within

6018-473: The affected areas. Newsom proclaimed a state of emergency for San Bernardino County on July 6. The California National Guard deployed 200 personnel to assist in relief operations. Power and water service was restored to Ridgecrest and roads were deemed safe by July 7; however, residents were advised to boil water for several days. Following the shock, (NAWS) Naval Air Weapons Station China Lake evacuated all non essential personnel and declared

6120-650: The area in and around the Coso Volcanic Field. The first large quake on July 4 registered M6.4 and the largest on July 5 registered M7.1. Within a week, more than 8000 (M1.0-4.5) smaller earthquakes had joined the swarm, though only 27 quakes larger than M4.5 occurred after the largest events. Surprisingly, there were no fatalities in California. Residents in Ridgecrest and neighboring unincorporated town Trona had moderate to severe property damage. Two structure fires, loss of power for up to 24 hours in some areas, and Trona

6222-547: The base as "not mission capable until further notice" in a statement published on the base's Facebook page on July 6. In addition, Dr. Lucy Jones said that the odds of another 7 M w   or above earthquake was a "1 in 10 chance", with a "50-50" chance of a 6 M w   hitting the Owens Valley. The NW-SE fault is believed to now have increased to between 25 and 30 miles in length. Many residents of Los Angeles County were not pleased when an earthquake early warning mobile app, ShakeAlertLA, did not alert them to either of

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6324-437: The body's interior and may break through the solid surface. For volcanism to occur, the temperature of the mantle must have risen to about half its melting point. At this point, the mantle's viscosity will have dropped to about 10 Pascal-seconds . When large scale melting occurs, the viscosity rapidly falls to 10 Pascal-seconds or even less, increasing the heat transport rate a million-fold. The occurrence of volcanism

6426-455: The case of water, increasing pressure decreases melting point until a pressure of 0.208 GPa is reached, after which the melting point increases with pressure. Flux melting occurs when the melting point is lowered by the addition of volatiles, for example, water or carbon dioxide. Like decompression melting, it is not caused by an increase in temperature, but rather by a decrease in melting point. Cryovolcanism , instead of originating in

6528-594: The city and opened two shelters. Fifteen patients at Ridgecrest Regional Hospital and residents in several apartment buildings were evacuated. Approximately 6,900 customers lost power near the epicenter: 6,000 in Ridgecrest and 900 in Searles Valley. A 4 in (10 cm) wide crack occurred along State Route 178 near Searles Valley and debris covered part of U.S. Route 395 . In Trona , several buildings sustained damage, water and gas lines broke, and power lines fell. Rockslides covered multiple roads around

6630-601: The community, blocking off mountain roads, including the section of State Route 178 that connects Bakersfield with Lake Isabella. In Los Angeles proper, power outages affected the Fashion District and Granada Hills . One person died in Pahrump, Nevada , when a lifted Jeep he was working under collapsed. Several fires broke out and five injuries were reported after the mainshock hit, most of them in Ridgecrest and Trona. 3,000 people were left without power in Ridgecrest and

6732-416: The cryomagma less dense), or with the presence of a densifying agent in the ice shell. Another is to pressurise the fluid to overcome negative buoyancy and make it reach the surface. When the ice shell above a subsurface ocean thickens, it can pressurise the entire ocean (in cryovolcanism, frozen water or brine is less dense than in liquid form). When a reservoir of liquid partially freezes, the remaining liquid

6834-538: The density of impact craters on the surface. Lava flows are widespread and forms of volcanism not present on Earth occur as well. Changes in the planet's atmosphere and observations of lightning have been attributed to ongoing volcanic eruptions, although there is no confirmation of whether or not Venus is still volcanically active. However, radar sounding by the Magellan probe revealed evidence for comparatively recent volcanic activity at Venus's highest volcano Maat Mons , in

6936-532: The difference in height between the basin and the height of the surrounding terrain could allow eruption of magma which otherwise would have stayed beneath the surface. A 2011 article showed that there would be zones of enhanced magma ascent at the margins of an impact basin. Not all of these mechanisms, and maybe even none, operate on a given body . Silicate volcanism occurs where silicate materials are erupted. Silicate lava flows, like those found on Earth, solidify at about 1000 degrees Celsius. A mud volcano

7038-412: The eastern side of the Coso Volcanic Field, 15 miles (24 km). September 30, 2009 to October 6, 2009 there have been 429 earthquakes ranging from 0.1 to 5.2. Some days have activity at about one tremor every minute. On October 2, 2009 there were three earthquakes, (5.2, 4.7, and a 4.9), all within one hour of each other. On July 4th and 5th, 2019 two large earthquakes sparked a surge of activity in

7140-433: The enrichment of magma at the top of a dike by gas which is released when the dike breaches the surface, followed by magma from lower down than did not get enriched with gas. The reason the dissolved gas in the magma separates from it when the magma nears the surface is due to the effects of temperature and pressure on gas solubility . Pressure increases gas solubility, and if a liquid with dissolved gas in it depressurises,

7242-432: The epicenter was Ridgecrest , home to 28,000 people. The foreshock originated along a strike-slip fault in the Eastern California Shear Zone , a region frequented by earthquake swarms, near the edge of Death Valley National Park . The rupture occurred along a 10 mi (16 km) section of an unspecified fault. Earth on either side of the fault was deformed, with lateral shifts of 6–8 in (15–20 cm) in

7344-450: The foreshock, and approximately 30 million people experienced the mainshock. At 10:02 a.m. PDT (17:02  UTC ) on July 4, 2019, a 4.0 M w   foreshock occurred about 6.8 mi (10.9 km) southwest of Searles Valley, California . A foreshock registering 6.4 M w   occurred at 10:33 a.m. PDT (17:33 UTC) 7.5 mi (12.1 km) southwest of Searles Valley. The most populated area near

7446-427: The form of ash flows near the summit and on the northern flank. However, the interpretation of the flows as ash flows has been questioned. There are several extinct volcanoes on Mars , four of which are vast shield volcanoes far bigger than any on Earth. They include Arsia Mons , Ascraeus Mons , Hecates Tholus , Olympus Mons , and Pavonis Mons . These volcanoes have been extinct for many millions of years, but

7548-605: The gas in the ash as it expands chills the magma fragments, often forming tiny glass shards recognisable as portions of the walls of former liquid bubbles. In more fluid magmas the bubble walls may have time to reform into spherical liquid droplets. The final state of the colloids depends strongly on the ratio of liquid to gas. Gas-poor magmas end up cooling into rocks with small cavities, becoming vesicular lava . Gas-rich magmas cool to form rocks with cavities that nearly touch, with an average density less than that of water, forming pumice . Meanwhile, other material can be accelerated with

7650-432: The gas will tend to exsolve (or separate) from the liquid. An example of this is what happens when a bottle of carbonated drink is quickly opened: when the seal is opened, pressure decreases and bubbles of carbon dioxide gas appear throughout the liquid. Fluid magmas erupt quietly. Any gas that has exsolved from the magma easily escapes even before it reaches the surface. However, in viscous magmas, gases remain trapped in

7752-462: The gas, becoming volcanic bombs . These can travel with so much energy that large ones can create craters when they hit the ground. A colloid of volcanic gas and magma can form as a density current called a pyroclastic flow . This occurs when erupted material falls back to the surface. The colloid is somewhat fluidised by the gas, allowing it to spread. Pyroclastic flows can often climb over obstacles, and devastate human life. Pyroclastic flows are

7854-481: The immediate vicinity. The exact fault it occurred on is uncertain with many small faults encompassing the region, though United States Geological Survey (USGS) seismologist Susan Hough stated it may have been the Little Lake Fault. Focused at a relatively shallow depth of 6.6 mi (10.7 km), the foreshock affected a large region populated by 20 million people. Residents near the epicenter reported that shaking lasted approximately 30 seconds. Shaking

7956-433: The lava rapidly loses viscosity, unlike silicate lavas like those found on Earth. When magma erupts onto a planet's surface, it is termed lava . Viscous lavas form short, stubby glass-rich flows. These usually have a wavy solidified surface texture. More fluid lavas have solidified surface textures that volcanologists classify into four types. Pillow lava forms when a trigger, often lava making contact with water, causes

8058-456: The limited span of the historical era. The most notable of these earthquakes is the 1872 Owens Valley earthquake , with an estimated magnitude of 7.4 M w (preferred; other estimates range as high as 7.9 ). The Owens Valley quake is believed to be the greatest earthquake on record and not just for California, but also for the western continental United States. In March 1946 an M L  6.3 earthquake struck near Walker Pass (crest of

8160-426: The magma even after they have exsolved, forming bubbles inside the magma. These bubbles enlarge as the magma nears the surface due to the dropping pressure, and the magma grows substantially. This fact gives volcanoes erupting such material a tendency to ‘explode’, although instead of the pressure increase associated with an explosion, pressure always decreases in a volcanic eruption. Generally, explosive cryovolcanism

8262-475: The northwestern corner of the Naval Weapons Center (NWC), where the OVF turns slightly to the east. At the south end of Rose Valley the Little Lake Fault – scene of the 2019 Ridgecrest earthquakes – strikes southeast from near Little Lake (a "locale" at the south end of Rose Valley) to run under the Naval Weapons Center. The surface trace of the Little Lake Fault is mapped through the northeast corner of

8364-672: The other terrestrial planets. It has a smooth surface, with mounds, hollows and folds. A volcanic eruption could just be a simple outpouring of material onto the surface of a planet, but they usually involve a complex mixture of solids, liquids and gases which behave in equally complex ways. Some types of explosive eruptions can release energy a quarter that of an equivalent mass of TNT . Volcanic eruptions on Earth have been consistently observed to progress from erupting gas rich material to gas depleted material, although an eruption may alternate between erupting gas rich to gas depleted material and vice versa multiple times. This can be explained by

8466-443: The possibility that the production of pressurised gas upon destabilisation of clathrate hydrates making contact with warm rising magma could produce an explosion that breaks through the surface, resulting in explosive cryovolcanism. If a fracture reaches the surface of an icy body and the column of rising water is exposed to the near-vacuum of the surface of most icy bodies, it will immediately start to boil, because its vapor pressure

8568-509: The pressure of the rock is greater than that of the dike at its bottom. So the magma thus pushes the crack upwards at its top, but the crack is squeezed closed at its bottom due to an elastic reaction (similar to the bulge next to a person sitting down on a springy sofa). Eventually, the tail gets so narrow it nearly pinches off, and no more new magma will rise into the crack. The crack continues to ascend as an independent pod of magma. This model of volcanic eruption posits that magma rises through

8670-648: The resource. The Coso Volcanic Field is one of the most seismically active regions in the United States, producing dozens of tremors in the M1 and M2 range each week. Tremors in the M3 range occur at a rate of 2–6 per month and M4 quakes occur two-three times each year. Recent activity in the M5 range happened in 1996 and 1998 when tremors of M5.3, M5.1, M5.2, and M5.0 occurred within a day of each other. These tremors were actually recorded along

8772-423: The rest are essentially aphyric . Obsidian is exposed locally on most extrusions, and analyses of fresh glass indicate that all of the rhyolite is of the so-called high-silica variety; SiO 2 content is essentially constant at 77 percent. Other major-element constituents are nearly invariant. However, trace-element contents vary and help define 7 age groups, each of unique chemical composition. Obsidian from

8874-458: The rest of Kern County. In Trona, severe damage was reported, with houses knocked off their foundations and numerous gas leaks. Roughly 50 homes were damaged in the town. Multiple rockslides also occurred, making all roads to the city impassable. Water was also in high demand. CalTrans once again closed State Route 178 after new cracks and rockslides had occurred. Overall damage is estimated in excess of $ 5.3 billion. Hours after

8976-473: The sequence) to the east of Ridgecrest. The first main shock (now deemed to be a foreshock ) occurred on Thursday, July 4 at 10:33 a.m. PDT , approximately 18 km (11.2 mi) ENE of Ridgecrest, and 13 km (8.1 mi) WSW of Trona , on a previously unnoticed NE-SW trending fault where it intersects the NW-SE trending Little Lake Fault Zone. This quake was preceded by several smaller earthquakes, and

9078-417: The shallow crust, in cryovolcanism, the water (cryomagmas tend to be water based) is denser than the ice above it. One way to allow cryomagma to reach the surface is to make the water buoyant, by making the water less dense, either through the presence of other compounds that reverse negative buoyancy, or with the addition of exsolved gas bubbles in the cryomagma that were previously dissolved into it (that makes

9180-416: The slower it loses heat. In larger bodies, for example Earth, this heat, known as primordial heat, still makes up much of the body's internal heat, but the Moon, which is smaller than Earth, has lost most of this heat. Another heat source is radiogenic heat, caused by radioactive decay . The decay of aluminium-26 would have significantly heated planetary embryos, but due to its short half-life (less than

9282-442: The solar system where volcanoes can be easily seen due to their high activity, Earth and Io. Its lavas are the hottest known anywhere in the Solar System, with temperatures exceeding 1,800 K (1,500 °C). In February 2001, the largest recorded volcanic eruptions in the Solar System occurred on Io. Europa , the smallest of Jupiter's Galilean moons , also appears to have an active volcanic system, except that its volcanic activity

9384-473: The southern end of the ECSZ the 1992 Landers earthquake , at magnitude M w  7.2 ( M s 7.8) was also the strongest earthquake in California since 1906. It was followed by a M w  7.2 ( M S 7.4) quake on a nearby fault, the 1999 Hector Mine earthquake . Following the Landers earthquake "a well-developed linear pattern of primary and triggered aftershocks" was observed that extended along

9486-480: The strongest of which measured 5.4 M w   at 4:07 a.m. PDT (11:07 UTC) on July 5. Shaking from this aftershock was felt as far north as Fresno , as far south as Laguna Hills (including Los Angeles), and as far east as Las Vegas, Nevada . No additional damage occurred from any of the aftershocks. The number of aftershocks within hours of the earthquake were unusually high, but not unprecedented. Thousands more aftershocks occurred following

9588-415: The surface, and the release of pressure causes more gas to exsolve, doing so explosively. The gas may expand at hundreds of metres per second, expanding upward and outward. As the eruption progresses, a chain reaction causes the magma to be ejected at higher and higher speeds. The violently expanding gas disperses and breaks up magma, forming a colloid of gas and magma called volcanic ash . The cooling of

9690-580: The town of Ridgecrest, California located in Kern County and west of Searles Valley (approximately 200 km [122 mi] north-northeast of Los Angeles ). They included three initial main shocks of M w magnitudes 6.4, 5.4, and 7.1, and many perceptible aftershocks , mainly within the area of the Naval Air Weapons Station China Lake . Eleven months later, a M w   5.5 aftershock took place (the largest aftershock of

9792-478: The volcanic fields was traded all the way to the California coast in San Diego , San Luis Obispo County , Santa Barbara, California , and throughout the Mojave Desert and regions further east. Archaeologists recognize at least four different geochemical subsources: Sugarloaf, West Sugarloaf, Joshua Ridge , and West Cactus Peak. These different subsources were used to varying degrees in different time periods, but

9894-439: The water to exsolve into gas. The elastic nature of the ice shell would likely prevent the fracture reaching the surface, and the crack would instead pinch off, enclosing the gas and liquid. The gas would increase buoyancy and could allow the crack to reach the surface. Even impacts can create conditions that allow for enhanced ascent of magma. An impact may remove the top few kilometres of crust, and pressure differences caused by

9996-459: The water would rise to its level of hydrostatic equilibrium, at about nine-tenths of the way to the surface. Tides which induce compression and tension in the ice shell may pump the water farther up. A 1988 article proposed a possibility for fractures propagating upwards from the subsurface ocean of Jupiter's moon Europa. It proposed that a fracture propagating upwards would possess a low pressure zone at its tip, allowing volatiles dissolved within

10098-614: Was a "1 in 20 chance" that the shock would be followed by larger earthquakes over the next few days. Jones also noted that the magnitude of additional shocks would also likely increase, with some possibly exceeding 5 M w  . The State Operations Center for the California Governor's Office of Emergency Services (Cal OES) was raised to its highest level by Governor Newsom to coordinate resources. The agency distributed cots, water, and food. Due to temperatures exceeding 100 °F (38 °C), Cal OES established cooling stations in

10200-488: Was felt as far north as Sacramento, California , eastward to Phoenix, Arizona , and as far south as Baja California , Mexico, with evacuations taking place in Mexicali and Tijuana . At 8:19 p.m. PDT on July 5, a larger 7.1 M w   earthquake occurred in the Ridgecrest area after being preceded by a 5.0 M w   foreshock 3 minutes prior, revealing the previous day's 6.4 M w   earthquake to have been

10302-452: Was followed by more than 1,400 detected aftershocks. The M 5.4 and M 7.1 quakes struck on Friday, July 5 at 4:08 a.m. and 8:19 p.m. PDT approximately 10 km (6 miles) to the northwest. The latter, now considered the mainshock, was the most powerful earthquake to occur in the state in 20 years (after the 1999 Hector Mine earthquake ). Subsequent aftershocks extended approximately 50 km (~30 miles) along

10404-473: Was without water. Highway 178, one of the two ways in or out of Trona was blocked from rockslides and impassable shifted sections of asphalt. Ridgecrest had declared a state of emergency as a result. One fatality was reported in Nevada in the following days. Earthquake swarms are common in the Coso area, often producing hundreds of tremors over periods as short as a few days. This brisk and robust seismic activity

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