Making Crack

[Nate J]

what makes big continuous cracks in rock?

i'm familiar with the freezing and expansion of rock causing cracks, but it doesn't seem likely that big continuous cracks (e.g. city park at Index on granite, or Supercrack at Indian Creek on sandstone) form that way. Maybe I'm wrong?

Does something geological explain the cracks? (Intrusion of different rock types deep underground)

It is something structural in the rock (eg the crystaline structure can support the weight and fractures)

 

Why do big rocks have cracks?

[JosephH]

Theirs not to make reply, theirs not to reason why, theirs but to do or fly

[ivan]

what happens if you take a cookie and put pressure on it, especially if it's on top of an irregular surface? it fractures.

[pink]

 

I smoke crack

 

Edited March 12, 2012 by pink

[chirp]

This crack was, as oral word goes, created by a engineering challenge to create a perfect split in the rock using blasting devices. If true, they succeeded.

 

[pink]

i love climbing in the splatte!

[chirp]

I loved Mountain Magazine!

[marc_leclerc]

I always thought baking soda was somehow involved.

[G-spotter]

what makes big continuous cracks in rock?

i'm familiar with the freezing and expansion of rock causing cracks, but it doesn't seem likely that big continuous cracks (e.g. city park at Index on granite, or Supercrack at Indian Creek on sandstone) form that way. Maybe I'm wrong?

Does something geological explain the cracks? (Intrusion of different rock types deep underground)

It is something structural in the rock (eg the crystaline structure can support the weight and fractures)

 

Why do big rocks have cracks?

 

Rock is formed at high pressure underground. What happens when that pressure is released when erosion brings that rock to the surface?

 

Some rocks are formed at high temperatures as a liquid magma. what happens when that magma cools? Remember for rocks volume (liquid) > volume (solid).

[hakioawa]

 

Rock is formed at high pressure underground. What happens when that pressure is released when erosion brings that rock to the surface?

 

Some rocks are formed at high temperatures as a liquid magma. what happens when that magma cools? Remember for rocks volume (liquid) > volume (solid).

 

This explains some fractures (e.g. the columns in Vantage), but not those in sedimentary rocks, nor the regional fracture patterns you see in some areas, such as the fins in the Fiery Furnace in Arches park.

 

The way to think about this is that these fractures are not actually big. You need to think at much larger scale. Cooled rock is fairly brittle. Lets say you have say a 10-100 mile unit of homogeneous rock (in plan view) that is say 200' thick. If you put an stress on it, over a long period of time, you'll find that the fractures tend to line up orthogonal (perpendicular) to the regional stress.

 

Take a look at this:

 

See how all the fractures are lined up and vertical? We can conclude that this area is being extended by "tectonic forces" orthogonal to the fractures. In this case I believe it is because a big blob (technical term) of salt a mile or so below is rising to the surface.