Large round boulders on hilltops

double postThis message has been edited by roxrkool, 10-16-2005 11:23 PM

How big are the boulders? And could you give an idea of where you live? That would help a lot.

I understand your desire to remain somewhat anonymous, however, without the slightest idea of where you are or what the geology is in your area, we are all left guessing. We really need to know how big the boulders are and what the formation looks like.Are the boulders in some sort of sandy and/or cobble matrix? Are the boulders in a lithified (hardened) or unconsolidated matrix? Do the boulders occur only with other boulders like in Coragyps' photo?There are many, many reasons why boulders can exist on tops of mountains. They can be the result of glacial/fluvial/alluvial/colluvial deposition, they can be pediment/landslide/debris flow deposits, or in situ erosion of igneous rocks (as pointed out by others).Honestly, an attempt to explain your particular occurrence of boulders is a bit like trying to guess your name.This message has been edited by roxrkool, 10-17-2005 06:59 PM

I'm not sure what you're trying to get at, Jacen. Could you elaborate a bit more? I'm not sure if you're referring to the boulders mentioned in the OP or your own experience.And actually, brennakimi makes a valid point. Depending on the size of the boulders, water can move them around quite easily (glaciers can move even bigger boulders further). Spring flash floods and other larger floods, say One Hundred Year Floods, are common. Cement these flood deposits, uplift them, and they could certainly be found weathering on tops of mountains. No need to actually 'push' the boulders uphill. These deposits leave tell-tale signs, however.Additionally, if you're seeing boulders as heavy as buildings in the city, you are most likely looking at in situ weathering of bedrock.That's why it's important for Christian to tell us how these boulders occur, how big they are, etc. They could be in situ weathering of bedrock or boulders derived from a depositional process.

Well, you're right of course, but then we still don't know what size boulders we're considering here since Christian hasn't offered up that information yet.I did state, though, that most likely any boulders as large as you're suggesting are the result of in situ weathering of bedrock. As Dblevins noted, weathering and spalling off along joints will cause some rock types to become roundish boulders. That's what is happening in coragyps' link. (I see in you agreed with this already.)A flood the size of Noah's might actually have enough force to move enormous boulders around (not sure building-sized boulders, though, probably depends on how big you're talking). However, material deposited by a mega-flood is going to display certain diagnostic characteristics, such as cross-beds, laminae, graded bedding, channeling, etc., likely forming at massive scales. Additionally, the material itself will be heterolithic, meaning the deposit will be comprised of a large variety of rock types derived from a huge source area. Boulders derived in situ are likely to be composed of one rock type; or at least a few very similar/related rock types. As I stated above, depending on the actual size of boulders, a mega-flood may be able to move and deposit enormous boulders. I was simply pointing out that it's not impossible to get sedimentologically deposited boulders on tops of mountains as opposed to ones created in situ. We might get lucky.This message has been edited by roxrkool, 10-18-2005 12:30 AM

Actually, he's correct. It's a result of chemical weathering along joints.See: images of spheroidal weathering and websites about spheroidal weatheringThis message has been edited by roxrkool, 10-18-2005 01:26 AM

Those boulders were most likely created in situ. There were not moved there by water or anything else - except maybe tectonism.

So what was your consensus, Christian? Were your questions answered adequately?

I am willing to admit I am wrong, but not based on anyone's unsupported opinions. I need to be shown and convinced why your or YEC theories are better than mainstream science. Simply saying, "I think it's stupid" is not good enough for me.And no, most people have not researched "everything," but sometimes people have a lot of experience in certain areas of science.