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Sacajawea Patera is a large, elongate
Sacajawea Patera is a large, elongate caldera
A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...
located in Western Ishtar Terra
Ishtar Terra is the second largest of the three continental terrae regions on the planet Venus, the others being Aphrodite Terra and Lada Terra.
It is a highland region named after the Akkadian goddess Ishtar, and is found in the north o ...
on the smooth plateau of Lakshmi Planum, on the planet Venus
Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...
. The image is centred at 64.5 degrees North latitude and 337 degrees East longitude. It is approximately wide at the base. Sacajawea is a depression approximately deep and in diameter; it is elongate in a southwest–northeast direction. The depression is bounded by a zone of circumferential curvilinear structures interpreted to be graben
In geology, a graben () is a depression (geology), depressed block of the Crust (geology), crust of a planet or moon, bordered by parallel normal faults.
Etymology
''Graben'' is a loan word from German language, German, meaning 'ditch' or 't ...
and fault scarps. These structures are spaced apart, are in width and up to in length.
Extending up to approximately in length from the southeast of the patera is a system of linear structures thought to represent a flanking rift zone along which the lateral injection and eruption of magma may have occurred. A shield edifice in diameter with a prominent central pit lies along the trend of one of these features.
The impact crater Zlata, approximately in diameter is located within the zone of graben to the northwest of the patera. Few flow features are observed in association with Sacajawea, possibly due to age and state of degradation of the flows. Mottled bright deposits in width are located near the periphery and in the center of the patera floor within local topographic lows. Diffuse patches of dark material approximately in width are observed southwest of the patera, superposed on portions of the surrounding graben.
The formation of Sacajawea is thought to be related to the drainage and collapse of a large magma chamber
A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it u ...
. Gravitational relaxation may have caused the resultant caldera to sag, producing the numerous faults and graben that circumscribe the patera. Regions of complex, highly deformed tessera
A tessera (plural: tesserae, diminutive ''tessella'') is an individual tile, usually formed in the shape of a square, used in creating a mosaic. It is also known as an abaciscus or abaculus.
Historical tesserae
In early antiquity, mo ...
-like terrain are located north and east of the patera and are seen in the upper portion of the image.
References
* Volcanoes of Venus {{Venus-stub