5
votes
Geology: What's make a group of bedrock a formation?
Basically a formation is just a layer or group of layers of rock that is both distinct enough to be identifiable in the field and large enough to show up on a geological map. Usually it is many nearly ...
- 7,026
5
votes
Why does calcium occur together with felsic rocks and magnesium with mafic rocks if calcium is denser than magnesium?
First off, calcium is more generally associated with mafic rocks than with felsic rocks. Mafic rocks often include calcium-rich plagioclase feldspars.
Calcium is actually less dense than magnesium ...
- 4,041
5
votes
What are the craters and mounds in this Missouri bedrock map?
While I can't confirm that it correlates perfectly to the points in the map, the answer may be that at least a subset of them are the same structures that Bretz proposed a theory for in 1950 (in "...
- 211
4
votes
Spatially-explicit global database of parent rock chemistry?
No such thing exists.
Some of the data you're looking for may be available from government geological surveys.
For example, the Australian state of New South Wales provides this in their online map ...
- 23.1k
3
votes
Why does calcium occur together with felsic rocks and magnesium with mafic rocks if calcium is denser than magnesium?
if calcium is denser than magnesium?
Because chemical element density has very little to do with whether that element sinks or floats.
The "things" that sink or float are "phases" ...
- 23.1k
3
votes
Could the LA County Museum of Art fall into the LaBrea Tar pit during an earthquake?
The two geological faults that may be responsible of large earthquake in proximity of the museum are:
Hollywood fault;
Santa Monica fault (actually many branches, but they all go together as Santa ...
- 459
3
votes
is there any technique developed that can estimate depth of bedrock?
A small scale seismic survey as well.
I remember as students we found the water table using a 100m refraction line and a sledge hammer sound source. Scale that up from ~5m to 100m you're going to ...
- 3,893
3
votes
Accepted
What caused those colorations in bedrock?
This answer is based on a cursory look at the 1:50000 Foglio Appiano, from the Geologic Map of Italy (in Italian Language only, as far as I can tell). As I pointed out in comment, I intend it as just ...
- 669
2
votes
Geology: What's make a group of bedrock a formation?
According to Wikipedia, and perfectly consistent with basic historical geological textbooks, a formation is:
...the fundamental unit of lithostratigraphy. A formation consists of a certain number of ...
- 2,813
2
votes
Does the existence of limestone nodules in a clay soil horizon indicate a limestone bedrock?
There are three possible sources for the reported limestone nodules from the clay horizon from colluvium and alluvium. First, as noted before, they could be either detrital gravel of limestone either ...
- 96
2
votes
Oldest to Newest Bedrock in the USA "road trip"
If you were hoping for a smooth succession from Archean all the way down to Quaternary, you're going to be disappointed. Geology is messier than rocks being serenely laid down continuously through ...
- 3,628
1
vote
Accepted
Question regarding underground man-made facilities
This question is not about earth science. If anything, it has more to do with engineering.
Strategic or critical defense or government infrastructure needs to be protected against explosive attacks, ...
- 24.8k
1
vote
Question regarding underground man-made facilities
It is possible, but three reasons at least play in favours of remote mountain locations:
It is easier to dig into mountains, because you can start with the excavation directly from the mountain side, ...
- 459
1
vote
is there any technique developed that can estimate depth of bedrock?
Sonar (passive or active) or ground penetrating radar with both work, it can also be estimated from a published geologic profile of the area which are often built from both in addition to drill data.
- 7,026
1
vote
Does the existence of limestone nodules in a clay soil horizon indicate a limestone bedrock?
I can offer a counter-example. What if your soil sample is taken from the site of some lost ancient Roman buildings? The Romans built plenty in northern Tunisia, and like using travertine limestone. A ...
- 3,376
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