Bedrock: How To Determine


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How can a person tell if the rock formations he/she is seeing is actual bedrock or just a rock formation close to the surface. From what I can gather it is possible to describe bedrock and rockhead like a cake and its icing. The actual cake is the bedrock and the icing is the rockhead. I can understand the layout, but how does a person know whether or not they are on actual bedrock?

For illustrative purposes, say it is a layered cake. The icing on the top is the surface soil. You dig through that and hit the cake (bedrock), but as you continue to dig you hit another layer of icing (soil), and so on. Is the top layer of cake the bedrock, or is it the second layer? I hope this makes at least a little bit of sense where someone can answer it for me. :blink:

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Hey Chris ,

Maybe someone will have a better answer but when you hit bedrock all digging will stop! (short of dynamite or a jack hammer)

But there are exceptions. If the bedrock in your area is decomposed badly enough you can still dig through it but still harder than the top soil. When you hit that kind of layer usually the soil will become a constant color such as decomposed granite.

Find what kind of bedrock is in the area of desire and watch for that. In placerville where Im at we have a combination of different types from DG to slate to serpentine and besalt and a few more. Mainly I think it comes down to research of your area.

Hope This helped a little!

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Hey Chris ,

Maybe someone will have a better answer but when you hit bedrock all digging will stop! (short of dynamite or a jack hammer)

But there are exceptions. If the bedrock in your area is decomposed badly enough you can still dig through it but still harder than the top soil. When you hit that kind of layer usually the soil will become a constant color such as decomposed granite.

Find what kind of bedrock is in the area of desire and watch for that. In placerville where Im at we have a combination of different types from DG to slate to serpentine and besalt and a few more. Mainly I think it comes down to research of your area.

Hope This helped a little!

Thank you for the reply. Every little bit of information helps and I appreciate all responses. I am a little over halfway through Chris Ralph's Fists Full of Gold and have learned a lot more than I thought I knew. I have yet to read the entire chapter on Geology so I am hoping that opens up my eyes more, too.

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Bedrock is anything that does not move at full flood state. Boulders the size of your truck WILL move at full flood state, bedrock will not. You won't be digging too much bedrock out.

I once found a sweet fishing hole in a real out of the way spot on a river. About 200 yards up a tributary near an old road crossing we found what looked like a early 50's Mercury. The vehicle was of course in pretty bad shape and half buried in the sand but the front bumper was like new! We didn't have the time, tools or will to pull the bumper but thought "maybe when we come back here next year we'll pull it". The next year we did go back, not to pull the bumper but just to fish and....the car was gone. We were surprised someone made it all the way back in there with a trailer and pull that huge car out and wondered how long it had been there to begin with? My Jeep had to work getting back in there, how did they get it out?

The last day of the trip we decided to hike down stream to get to some real remote areas inside the canyon. About a mile and a half down stream we found our Mercury. And guess what, she was sitting right side up totally filled with mud, the roof and body crushed but that bumper was still looking pretty damm good.

In one year the vehicle had moved over a mile downstream. It makes me wonder really how far can gold move from it's source over many years????? :blink:

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Bedrock is anything that does not move at full flood state. Boulders the size of your truck WILL move at full flood state, bedrock will not. You won't be digging too much bedrock out.

I once found a sweet fishing hole in a real out of the way spot on a river. About 200 yards up a tributary near an old road crossing we found what looked like a early 50's Mercury. The vehicle was of course in pretty bad shape and half buried in the sand but the front bumper was like new! We didn't have the time, tools or will to pull the bumper but thought "maybe when we come back here next year we'll pull it". The next year we did go back, not to pull the bumper but just to fish and....the car was gone. We were surprised someone made it all the way back in there with a trailer and pull that huge car out and wondered how long it had been there to begin with? My Jeep had to work getting back in there, how did they get it out?

The last day of the trip we decided to hike down stream to get to some real remote areas inside the canyon. About a mile and a half down stream we found our Mercury. And guess what, she was sitting right side up totally filled with mud, the roof and body crushed but that bumper was still looking pretty damm good.

In one year the vehicle had moved over a mile downstream. It makes me wonder really how far can gold move from it's source over many years????? :blink:

Wow, that is crazy. Being a volunteer firefighter years ago I had the opportunity to assist in a few SWR's and it totally amazed me at the sheer power of water at high speeds. What is real amazing is that not only did it move over a mile and a half downstream, but it did so while navigating and conquering obstacles (boulders, logs, etc.) along the way.

Now the question is...........did you get the bumper? :D

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The best thing is is to go out with a seasoned fellow and have him show you bedrock and explain it to you while on site.Once you know it ,it's ingrained.Not just on the creek/river bottoms but also the hillsides if any,and the flats.

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The best thing is is to go out with a seasoned fellow and have him show you bedrock and explain it to you while on site.Once you know it ,it's ingrained.Not just on the creek/river bottoms but also the hillsides if any,and the flats.

Dave, that is exactly what I am hoping to be able to do sometime. One way or the other I will get good at this stuff. I can read all about the stuff, but in the books it just doesn't make any sense to me. it is so true that a picture is worth a thousand words. Thanks for the reply.

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Hey Chris,

Bedrock is also called Country rock. The country rock (or bedrock) you see poking out on the hillsides is the bedrock, or the hard surface of the Earth. Bedrock or Country Rock can be any of the three rock types -

Igneous Rocks - are crystalline solids which form directly from the cooling of magma. This is an exothermic process (it loses heat) and involves a phase change from the liquid to the solid state. The earth is made of igneous rock - at least at the surface where our planet is exposed to the coldness of space. Igneous rocks are given names based upon two things: composition (what they are made of) and texture (how big the crystals are).

Sedimentary Rocks - In most places on the surface, the igneous rocks which make up the majority of the crust are covered by a thin veneer of loose sediment, and the rock which is made as layers of this debris get compacted and cemented together. Sedimentary rocks are called secondary, because they are often the result of the accumulation of small pieces broken off of pre-existing rocks. There are three main types of sedimentary rocks; clastic, chemical and organic.

Metamorphic Rocks - The metamorphics get their name from "meta" (change) and "morph" (form). Any rock can become a metamorphic rock. All that is required is for the rock to be moved into an environment in which the minerals which make up the rock become unstable and out of equilibrium with the new environmental conditions. In most cases, this involves burial which leads to a rise in temperature and pressure. The metamorphic changes in the minerals always move in a direction designed to restore equilibrium. Common metamorphic rocks include slate, schist, gneiss, and marble.

P.S. Been trying to catch up with you about the stuff you wanted to order. Get back with me if you get a chance, or shoot me over a PM.

Hope this information helps a bit.

Rob Allison

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