Volcanic features
The dark and relatively featureless lunar plains that can clearly be seen with the naked eye are called maria (Latin for "seas"; singular mare), because they were believed by ancient astronomers to be filled with water. They are now known to be vast solidified pools of ancient basaltic lava. Although similar to terrestrial basalts, the mare basalts have much higher abundances of iron and are completely lacking in minerals altered by water.The majority of these lavas erupted or flowed into the depressions associated with impact basins. Several geologic provinces containing shield volcanoes and volcanic domes are found within the near side maria.
Evidence of young lunar volcanism.
Maria are found almost exclusively on the near side of the Moon, covering 31% of the surface on the near side, compared with a few scattered patches on the far side covering only 2%.This is thought to be due to a concentration of heat-producing elements under the crust on the near side, seen on geochemical maps obtained by Lunar Prospector's gamma-ray spectrometer, which would have caused the underlying mantle to heat up, partially melt, rise to the surface and erupt.[40][54][55] Most of the Moon's mare basalts erupted during the Imbrian period, 3.0–3.5 billion years ago, although some radiometrically dated samples are as old as 4.2 billion years.The youngest eruptions, dated by crater counting, appeared to have been only 1.2 billion years ago.However, in 2006 study of Ina, a tiny crater inLacus Felicitatis, identified jagged, relatively dust-free features that, due to the lack of erosion by infalling debris, appeared to be only 2 million years old. Moonquakes and releases of gas also indicate some continued lunar activity. In 2014 NASA announced "widespread evidence of young lunar volcanism" at 70 irregular mare patches identified by the Lunar Reconnaissance Orbiter, some less than 50 million years old, raising the possibility of a much warmer lunar mantle than previously believed, at least on the near side where the deep crust is substantially warmer due to the greater concentration of radioactive elements.Just prior to this, evidences has been presented for 2–10 million years younger basaltic volcanism inside Lowell crater,Orientale basin, located in the transition zone of the near to the far side of the Moon. An initially hotter mantle and/or local enrichment of heat-producing elements in the mantle could be responsible for prolonged activities also on the far side in the Orientale basin.
The lighter-coloured regions of the Moon are called terrae, or more commonly highlands, because they are higher than most maria. They have been radiometrically dated to having formed 4.4 billion years ago, and may represent plagioclase cumulates of the lunar magma ocean.In contrast to Earth, no major lunar mountains are believed to have formed as a result of tectonic events.
The concentration of mare on the Near Side likely reflects the substantially thicker crust of the highlands of the Far Side, which may have formed in a slow-velocity impact of a second terran moon a few tens of millions of years after their formation.
ลักษณะการทำภูเขาไฟมืด และค่อนข้างแก่การผักผ่อนจันทรคติราบที่สามารถมองเห็นได้ ด้วยตาเปล่าอย่างชัดเจนเรียกว่า maria (ภาษาละตินใน "ทะเล" เอกพจน์แมร์), เนื่องจากพวกเขาถูกเชื่อว่า โดยนักดาราศาสตร์โบราณเต็มไป ด้วยน้ำ ตอนนี้พวกเขาเรียกว่าเป็น สระที่แข็งใหญ่ของลาวา basaltic โบราณ แม้ว่าคล้ายกับ basalts ภาคพื้น basalts แมร์มี abundances สูงมากของเหล็ก และไม่มีอย่างสมบูรณ์ในการเปลี่ยนแปลง ด้วยน้ำแร่ ส่วนใหญ่เหล่านี้ lavas ปะทุ หรือไหลลงในทรายที่เชื่อมโยงกับผลกระทบอ่างล่างหน้า พบจังหวัดธรณีวิทยาหลายโล่ภูเขาและภูเขาไฟ domes ในด้านใกล้มาเรียหลักฐานของจันทรคติ volcanism หนุ่มMaria are found almost exclusively on the near side of the Moon, covering 31% of the surface on the near side, compared with a few scattered patches on the far side covering only 2%.This is thought to be due to a concentration of heat-producing elements under the crust on the near side, seen on geochemical maps obtained by Lunar Prospector's gamma-ray spectrometer, which would have caused the underlying mantle to heat up, partially melt, rise to the surface and erupt.[40][54][55] Most of the Moon's mare basalts erupted during the Imbrian period, 3.0–3.5 billion years ago, although some radiometrically dated samples are as old as 4.2 billion years.The youngest eruptions, dated by crater counting, appeared to have been only 1.2 billion years ago.However, in 2006 study of Ina, a tiny crater inLacus Felicitatis, identified jagged, relatively dust-free features that, due to the lack of erosion by infalling debris, appeared to be only 2 million years old. Moonquakes and releases of gas also indicate some continued lunar activity. In 2014 NASA announced "widespread evidence of young lunar volcanism" at 70 irregular mare patches identified by the Lunar Reconnaissance Orbiter, some less than 50 million years old, raising the possibility of a much warmer lunar mantle than previously believed, at least on the near side where the deep crust is substantially warmer due to the greater concentration of radioactive elements.Just prior to this, evidences has been presented for 2–10 million years younger basaltic volcanism inside Lowell crater,Orientale basin, located in the transition zone of the near to the far side of the Moon. An initially hotter mantle and/or local enrichment of heat-producing elements in the mantle could be responsible for prolonged activities also on the far side in the Orientale basin.ภูมิภาคไฟแช็กสีของดวงจันทร์เรียกว่า terrae หรือมากกว่าปกติไฮแลนด์ เนื่องจากจะสูงกว่ามาเรียส่วนใหญ่ พวกเขาได้รับการลง radiometrically จะมีเกิดขึ้น 4.4 พันล้านปี และอาจเป็นตัวแทน plagioclase cumulates ของมหาสมุทรหินหนืดจันทรคติ ตรงข้ามโลก ภูเขาดวงใหญ่ไม่เชื่อว่าได้เกิดขึ้นจากเหตุการณ์ธรณีความเข้มข้นของแมร์ด้านใกล้อาจสะท้อนถึงเปลือกหนามากของไฮแลนด์ของไกลด้าน ซึ่งอาจมีขึ้นในผลกระทบต่อความเร็วช้าของดวงสภาพภูมิประเทศสองกี่สิบล้านปีหลังจากการก่อตัวของพวกเขา
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