| 词条 | Shimada Seamount |
| 释义 |
Shimada Seamount is a seamount in the Pacific Ocean. Shimada seamount lies southwest of Baja California Sur. It is a shallow seamount, reaching a depth of {{convert|30|m}} below sea level{{sfn|GARDNER|DEAN|BLAKELY|1984|p=855}} and is a regular single-peaked mountain with a westerly spur and little relief otherwise. At {{convert|180|m}} depth lies a platform.{{sfn|GARDNER|DEAN|BLAKELY|1984|p=856}} Talus deposits surround the seamount at its base. The seafloor underneath Shimada is between 18-21 million years old and lies at a depth of about {{convert|4100|m}}; other than abyssal hills up to {{convert|1|km}} Shimada is isolated.{{sfn|GARDNER|DEAN|BLAKELY|1984|p=856}} Volcanic rocks taken from Shimada are considered to be icelandites. Most seamounts form at mid-ocean ridges, but hotspots and transform faults can also produce seamounts.{{sfn|GARDNER|DEAN|BLAKELY|1984|p=855}} These mechanisms cannot really explain the origin of Shimada Seamount, however;{{sfn|GARDNER|DEAN|BLAKELY|1984|p=856}} it may be part of a hotspot trace.{{sfn|GARDNER|DEAN|BLAKELY|1984|p=862}} Evidence in drill cores around the seamount and the appearance of the summit area,{{sfn|GARDNER|DEAN|BLAKELY|1984|p=861}} plus the presence of thin manganese crusts implies an age of about 10,000 for some volcanic rocks and the rocks are too young to be dated by potassium-argon dating, all indicate that volcanic activity at Shimada is of late Quaternary-Holocene age.{{sfn|GARDNER|DEAN|BLAKELY|1984|p=859}} Possibly alive Lithothamnium corals have been dredged from {{convert|110|-|130|m}} depth.{{sfn|GARDNER|DEAN|BLAKELY|1984|p=858}} See also
References}} Sources{{refbegin}}
2 : Seamounts of the Pacific Ocean|Quaternary volcanoes |
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