Accepted author manuscript, 821 KB, PDF document
Available under license: CC BY-NC: Creative Commons Attribution-NonCommercial 4.0 International License
Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Ina pit crater on the Moon
T2 - extrusion of waning-stage lava lake magmatic foam results in extremely young crater retention ages
AU - Qiao, Le
AU - Head, James
AU - Wilson, Lionel
AU - Xiao, Long
AU - Kreslavsky, Mikhail
AU - Dufek, Josef
PY - 2017/5
Y1 - 2017/5
N2 - The enigmatic Ina feature on the Moon was recently interpreted to represent extrusive basaltic volcanic activity within the past 100 m.y. of lunar history, an extremely young age for volcanism on the Moon. Ina is a 2 × 3 km D-shaped depression that consists of a host of unusual bleb-like mounds surrounded by a relatively optically fresh hummocky and blocky floor. Documentation of magmatic-volcanic processes from shield volcano summit pit craters in Hawai’i and new insights into shield-building and dike evolution processes on the Moon provide important perspectives on the origin of Ina. We show that the size, location, morphology, topography, and optical maturity of Ina are consistent with an origin as a subsided summit pit crater lava lake on top of a broad ~22-km-diameter, ~3.5-b.y.-old shield volcano. New theoretical treatments of lunar shield-building magmatic dike events predict that waning-stage summit activity was characterized by the production of magmatic foam in the dike and lake; the final stages of dike stress relaxation and closure cause the magmatic foam to extrude to the surface through cracks in the lava lake crust to produce the mounds. The high porosity of the extruded foams (>75%) altered the nature of subsequent impact craters (the aerogel effect), causing them to be significantly smaller in diameter, which could bias the crater-derived model ages. Accounting for this effect allows for significantly older model ages, to ~3.5 b.y., contemporaneous with the underlying shield volcano. Thus extremely young volcanic eruptions are not required to explain the unusual nature of Ina.
AB - The enigmatic Ina feature on the Moon was recently interpreted to represent extrusive basaltic volcanic activity within the past 100 m.y. of lunar history, an extremely young age for volcanism on the Moon. Ina is a 2 × 3 km D-shaped depression that consists of a host of unusual bleb-like mounds surrounded by a relatively optically fresh hummocky and blocky floor. Documentation of magmatic-volcanic processes from shield volcano summit pit craters in Hawai’i and new insights into shield-building and dike evolution processes on the Moon provide important perspectives on the origin of Ina. We show that the size, location, morphology, topography, and optical maturity of Ina are consistent with an origin as a subsided summit pit crater lava lake on top of a broad ~22-km-diameter, ~3.5-b.y.-old shield volcano. New theoretical treatments of lunar shield-building magmatic dike events predict that waning-stage summit activity was characterized by the production of magmatic foam in the dike and lake; the final stages of dike stress relaxation and closure cause the magmatic foam to extrude to the surface through cracks in the lava lake crust to produce the mounds. The high porosity of the extruded foams (>75%) altered the nature of subsequent impact craters (the aerogel effect), causing them to be significantly smaller in diameter, which could bias the crater-derived model ages. Accounting for this effect allows for significantly older model ages, to ~3.5 b.y., contemporaneous with the underlying shield volcano. Thus extremely young volcanic eruptions are not required to explain the unusual nature of Ina.
U2 - 10.1130/G38594.1
DO - 10.1130/G38594.1
M3 - Journal article
VL - 45
SP - 455
EP - 458
JO - Geology
JF - Geology
SN - 0091-7613
IS - 5
ER -