View Full Version : A question for the Show

2009-Mar-17, 04:14 AM
mm never thought of that, the answer might be out there but i thought os asking it
we all know why there are craters on the moon.... but why there are trenches on the moon?
I had gone over several detailed moon surface images and seen there are trenches.. and could not see how geologically this could have happened..

Any idea?

2009-Mar-17, 08:15 AM
Even the moon was geologically active once. Plate Tectonics maybe? Or differential cooling?

2009-Mar-17, 09:54 AM
how would tectonics work if the moon does not have a solid core....as far as i remember the most valid theory for moon creation was that an object collided with earth and chunk of soft material flew in space and by time it created the moon, leaving the earth with a core and the moon baked with no core and no volatiles....

Whats differential Cooling?

Killer Bee
2009-Mar-17, 12:08 PM
3.9 billion years ago the mantel in the moon was still hot. we were bombarded with junk from space pretty heavily at the time and when the crater would puncture the crust, lava would fill the crater and naturally make flows. This is what you see even now

2009-Mar-17, 12:53 PM
And you don't need a solid core for plate tectonics. You would need a liquid core and for sure when the moon was created through this impact the rock would melt, clump together and be liquid for a while, slowly cooling off from outside to inside and thusly provide a crust wich can be active on the molten magma

2009-Mar-18, 12:12 AM
There were no plate tectonics on the moon (or at least no evidence for it). By "trenches," I assume you mean wrinkle ridges (http://en.wikipedia.org/wiki/Wrinkle_ridge) which are volcanic features due to cooling lava.

2009-Mar-18, 12:39 AM
Perhaps flowing lava?

2009-Mar-18, 12:51 AM
I forgot to mention graben in addition to wrinkle ridges. Graben are kinda the opposite - they're due to the surface spreading apart and material sinking, while the wrinkle ridges are due to the surface contracting and material being raised up.

2009-Mar-18, 03:49 AM
that was a nice answer..This is what i meant by trenches
I hope the attachment works..

2009-Mar-18, 04:26 AM
Ah. I was forgetting my classification hierarchy. Grooves/troughs/trenches fall under the general category of a "rille" (German for "groove"). A graben that I mentioned before is a type of rille that is associated with crustal stretching.

What you have circled is another type of rille, called a "sinuous rille," and it is very likely a collapsed lava tube. This forms when lava that filled a channel vacates that channel so it is now hollow. The strength of the material making the now hollow tube is not enough to support the weight above it, so it collapses.

There are HUGE ones on the volcanic constructs on Mars. They're also visible on Earth and it is thought that MESSENGER has finally imaged them on Mercury (Mariner 10 did not have sufficient resolution).