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Ejecta Blanket
An ejecta blanket is a generally symmetrical apron of ejecta that surrounds an impact crater; it is layered thickly at the crater's rim and thin to discontinuous at the blanket's outer edge. The impact cratering is one of the basic surface formation mechanisms of the solar system bodies (including the Earth) and the formation and emplacement of ejecta blankets are the fundamental characteristics associated with impact cratering event. The ejecta materials are considered as the transported materials beyond the transient cavity formed during impact cratering regardless of the state of the target materials. Formation A blanket of ejecta is formed during the formation of meteor impact cratering and is composed usually of the materials of that are ejected from the cratering process. Ejecta materials are deposited on the preexisting layer of target materials and therefore it form an inverted stratigraphy than the underlying bedrock. In some cases, the excavated fragment of ejects ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ejecta
Ejecta (from the Latin: "things thrown out", singular ejectum) are particles ejected from an area. In volcanology, in particular, the term refers to particles including pyroclastic materials (tephra) that came out of a volcanic explosion and magma eruption volcanic vent, or crater, has traveled through the air or under water, and fell back on the ground surface or on the ocean floor. Volcanology Typically in volcanology, ejecta is a result of explosive eruptions. In an explosive eruption, large amounts of gas are dissolved in extremely viscous lava; this lava froths to the surface until the material is expelled rapidly due to the trapped pressure. Sometimes in such an event a lava plug or volcanic neck forms from lava that solidifies inside a volcano's vent, causing heat and pressure to build up to an extreme with no way to escape. When the blockage breaks and cannot sustain itself any longer, a more violent eruption occurs, which allows materials to be ejected out of the volc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Lunar impact craters range from microscopic craters on lunar rocks returned by the Apollo Program and small, simple, bowl-shaped depressions in the lunar regolith to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth. Impact craters are the dominant geographic features on many solid Solar System objects including the Moon, Mercury, Callisto, Ganymede and most small moons and asteroids. On other planets and moons that experience more active surface geological processes, such as Earth, Venus, Europa, Io and Titan, visible impact craters are less common because they become eroded ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratigraphy
Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostratigraphy (lithologic stratigraphy), biostratigraphy (biologic stratigraphy), and chronostratigraphy (stratigraphy by age). Historical development Catholic priest Nicholas Steno established the theoretical basis for stratigraphy when he introduced the law of superposition, the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment. The first practical large-scale application of stratigraphy was by William Smith (geologist), William Smith in the 1790s and early 19th century. Known as the "Father of English geology", Smith recognized the significance of Stratum, strata or rock layering and the importance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Crater
Secondary craters are impact craters formed by the ejecta that was thrown out of a larger crater. They sometimes form radial crater chains. In addition, secondary craters are often seen as clusters or rays surrounding primary craters. The study of secondary craters exploded around the mid-twentieth century when researchers studying surface craters to predict the age of planetary bodies realized that secondary craters contaminated the crater statistics of a body's crater count. Formation When a velocity-driven extraterrestrial object impacts a relatively stationary body, an impact crater forms. Initial crater(s) to form from the collision are known as primary craters or impact craters. Material expelled from primary craters may form secondary craters (secondaries) under a few conditions: # Primary craters must already be present. # The gravitational acceleration of the extraterrestrial body must be great enough to drive the ejected material back toward the surface. # The velocity b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Event
An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect. When large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, though atmospheres mitigate many surface impacts through atmospheric entry. Impact craters and Impact structure, structures are dominant landforms on many of the Solar System's solid objects and present the strongest empirical evidence for their frequency and scale. Impact events appear to have played a significant role in the Formation and evolution of the Solar System, evolution of the Solar System since its formation. Major impact events have significantly shaped History of the Earth, Earth's history, and have been implicated in the giant impact theory, formation of the Earth� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lunar And Planetary Institute
The Lunar and Planetary Institute (LPI) is a scientific research institute dedicated to study of the Solar System, its formation, evolution, and current state. The Institute is part of the Universities Space Research Association (USRA) and is supported by the Science Mission Directorate of the National Aeronautics and Space Administration (NASA). Located at 3600 Bay Area Boulevard in Houston, Texas, the LPI maintains an extensive collection of lunar and planetary data, carries out education and public outreach programs, and offers meeting coordination and publishing services. The LPI sponsors and organizes several workshops and conferences throughout the year, including the Lunar and Planetary Science Conference (LPSC) held in March in the Houston area. History In his March 1968 speech at the Manned Spacecraft Center (MSC) in Houston, Texas, President Lyndon B. Johnson announced the formation of the Lunar Science Institute (LSI). "We will welcome here all who are interested i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Houston, Texas
Houston (; ) is the most populous city in Texas, the most populous city in the Southern United States, the fourth-most populous city in the United States, and the sixth-most populous city in North America, with a population of 2,304,580 in 2020. Located in Southeast Texas near Galveston Bay and the Gulf of Mexico, it is the seat and largest city of Harris County and the principal city of the Greater Houston metropolitan area, which is the fifth-most populous metropolitan statistical area in the United States and the second-most populous in Texas after Dallas–Fort Worth. Houston is the southeast anchor of the greater megaregion known as the Texas Triangle. Comprising a land area of , Houston is the ninth-most expansive city in the United States (including consolidated city-counties). It is the largest city in the United States by total area whose government is not consolidated with a county, parish, or borough. Though primarily in Harris County, small portions of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Lunar impact craters range from microscopic craters on lunar rocks returned by the Apollo Program and small, simple, bowl-shaped depressions in the lunar regolith to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth. Impact craters are the dominant geographic features on many solid Solar System objects including the Moon, Mercury, Callisto, Ganymede and most small moons and asteroids. On other planets and moons that experience more active surface geological processes, such as Earth, Venus, Europa, Io and Titan, visible impact craters are less common because they become eroded ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Impact Craters On Earth
This list of impact craters on Earth contains a selection of the 190 confirmed craters given in the Earth Impact Database as of 2017. To keep the lists manageable, only the largest craters within a time period are included. Alphabetical lists for different continents can be found under Craters by continent below. Confirmed impact craters listed by size and age These features were caused by the collision of meteors (consisting of large fragments of asteroids) or comets (consisting of ice, dust particles and rocky fragments) with the Earth. For eroded or buried craters, the stated diameter typically refers to the best available estimate of the original rim diameter, and may not correspond to present surface features. Time units are either in ka (thousands) or Ma (millions) of years. 10 ka or less Less than ten thousand years old, and with a diameter of or more. The EID lists fewer than ten such craters, and the largest in the last 100,000 years (100 ka) is the Rio Cuarto c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Craters On Mercury
This is a list of named craters on Mercury, the innermost planet of the Solar System ''(for other features, see list of geological features on Mercury)''. Most Mercurian craters are named after famous writers, artists and composers. According to the rules by IAU's Working Group for Planetary System Nomenclature, all new craters must be named after an artist that was famous for more than fifty years, and dead for more than three years, before the date they are named. Craters larger than 250 km in diameter are referred to as "basins" ''(also see )''. As of 2021, there are 414 named Mercurian craters, a small fraction of the total number of named Solar System craters, most of which are lunar, Martian and Venerian craters. Other, non-planetary bodies with numerous named craters include Callisto ( 141), Ganymede ( 131), Rhea (128), Vesta (90), Ceres (90), Dione (73), Iapetus (58), Enceladus (53), Tethys (50) and Europa ( 41). For a full list, ''see List of craters in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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