Difference between revisions of "February 23, 2004"
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=Rocks and Time on the Moon= | =Rocks and Time on the Moon= | ||
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| − | + | <td colspan="2"><div align="center"> | |
| − | + | [[File:LPOD-2004-02-23.jpeg|LPOD-2004-02-23.jpeg]]</div> | |
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| − | + | <td><div align="center" span class="main_sm">Image Credit: [mailto:tychocrater@yahoo.com CA Wood] based on Figure 7 of Wilhelms (1987)</div></td> | |
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<table class="story" border="0" bgcolor="#FFFFFF" width="90%" cellpadding="10" align="center"><tr><td> | <table class="story" border="0" bgcolor="#FFFFFF" width="90%" cellpadding="10" align="center"><tr><td> | ||
| − | + | <p class="story" align="center"><b>Rocks and Time on the Moon </b></p> | |
| − | + | <p class="story" align="left"> | |
| − | + | What we see on the Moon are rock units, many of which were formed instantaneously. For example, the crater | |
| − | + | Copernicus disrupted the existing lunar surface and spread deposits as rays and secondary craters - new rock | |
| − | + | units. Copernicus is one of the largest young craters and its rays define a a chronologic instant in lunar | |
| − | + | history that we can use to relatively date other rock units. We can safely infer that the surface of Mare Imbrium | |
| − | + | must be older than Copernicus because the mare is crossed by Copernicus' rays and secondary craters. The formation | |
| − | + | of large impact basins are much larger, almost Moon wide, events that are used to define time boundaries. Ejecta | |
| − | + | deposits from the two youngest large basins - Orientale and Imbrium - are nearly instantaneously created rock | |
| − | + | units. During the 1960s the US Geologic Survey made observations such as these and developed a stratigraphic | |
| − | + | history of the Moon. That history is summarized in the Survey's Geologic | |
| − | + | [LPOD-2004-02-03.htm Map of the Moon] and in this chart whose colors approximately match those of | |
| − | + | the Map. The names Copernican, Eratosthenian, Imbrium, Nectarian and pre-Nectarian are commonly used by lunar | |
| − | + | scientist to describe periods of lunar history. Note how much activity was squeezed into the first 700 million | |
| − | + | years, and how little has happened during the last three billion! | |
| − | + | </p> | |
| − | + | <p class="story"><b>Related Links:</b><br> | |
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The Geologic History of the Moon by Don E. Wilhelms. US Geol. Surv. PP 1348 (1987).</p> | The Geologic History of the Moon by Don E. Wilhelms. US Geol. Surv. PP 1348 (1987).</p> | ||
| − | + | <p class="story"> <b>Tomorrow's LPOD:</b> An Amateur's Moon</p> | |
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| − | + | <p align="center" class="main_titles"><b>Author & Editor:</b><br> | |
| − | + | [mailto:tychocrater@yahoo.com Charles A. Wood]</p> | |
| − | + | <p align="center" class="main_titles"><b>Technical Consultant:</b><br> | |
| − | + | [mailto:anthony@perseus.gr Anthony Ayiomamitis]</p> | |
| − | + | <p align="center" class="main_titles"><b>A service of:</b><br> | |
| − | + | [http://www.observingthesky.org/ ObservingTheSky.Org]</p> | |
| − | + | <p align="center" class="main_titles"><b>Visit these other PODs:</b> <br> | |
| − | + | [http://antwrp.gsfc.nasa.gov/apod/astropix.html Astronomy] | [http://www.msss.com/ Mars] | [http://epod.usra.edu/ Earth]</p></td> | |
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===COMMENTS?=== | ===COMMENTS?=== | ||
Click on this icon [[image:PostIcon.jpg]] at the upper right to post a comment. | Click on this icon [[image:PostIcon.jpg]] at the upper right to post a comment. | ||
Revision as of 18:16, 4 January 2015
Rocks and Time on the Moon
 |
Image Credit: CA Wood based on Figure 7 of Wilhelms (1987) |
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Rocks and Time on the Moon What we see on the Moon are rock units, many of which were formed instantaneously. For example, the crater Copernicus disrupted the existing lunar surface and spread deposits as rays and secondary craters - new rock units. Copernicus is one of the largest young craters and its rays define a a chronologic instant in lunar history that we can use to relatively date other rock units. We can safely infer that the surface of Mare Imbrium must be older than Copernicus because the mare is crossed by Copernicus' rays and secondary craters. The formation of large impact basins are much larger, almost Moon wide, events that are used to define time boundaries. Ejecta deposits from the two youngest large basins - Orientale and Imbrium - are nearly instantaneously created rock units. During the 1960s the US Geologic Survey made observations such as these and developed a stratigraphic history of the Moon. That history is summarized in the Survey's Geologic [LPOD-2004-02-03.htm Map of the Moon] and in this chart whose colors approximately match those of the Map. The names Copernican, Eratosthenian, Imbrium, Nectarian and pre-Nectarian are commonly used by lunar scientist to describe periods of lunar history. Note how much activity was squeezed into the first 700 million years, and how little has happened during the last three billion! Related Links: Tomorrow's LPOD: An Amateur's Moon |
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Author & Editor: Technical Consultant: A service of: |
COMMENTS?
Click on this icon File:PostIcon.jpg at the upper right to post a comment.
