Plate Tectonics and Impact Craters

[Taranofsky]

effing craters: how do they work?

just kidding.

but seriously…I think we're all familiar with the method of plate tectonics

if the continents drifted apart over millions of years

creating new crust in their wake

why are there those massive craters left over from millions of years ago, like the one off the coast of the Yucatán Peninsula? Shouldn't the new crust have filled that in?

 

 

help me out with this, thanks, I keep wondering about it

[Ophiolite]

Are these rocks off the Yucatan peninsula oceanic, or continental?

If they are continental, do continental rocks generally get significantly subducted?

If they are oceanic, what age are they?

What is the age of the impact crater?

Globally are more impact craters found in oceanic or continental crust?

What is the age of the oldest oceanic crust?

What is the age of the oldest confirmed continental impact crater?

 

If you can answer these questions (happy googling) then you will have the answer to your own question. Ask specifics if you are having any difficulties.

[Taranofsky]

You gave me good advice, and it turn out I was right to be confused (the caldera lies close to a fault)

but it turns out the impact craters has no more remnant physical data, but that it is simply an immense depression,

morphed by the destructive force beyond 'repair' by new crust forming, and actually leaving a measurable changes in gravity to be detected.

If that doesn't sound right to you, let me know, but it clears some things up for me.

 

Are these rocks off the Yucatan peninsula oceanic, or continental?

If they are continental, do continental rocks generally get significantly subducted?

If they are oceanic, what age are they?

What is the age of the impact crater?

Globally are more impact craters found in oceanic or continental crust?

What is the age of the oldest oceanic crust?

What is the age of the oldest confirmed continental impact crater?

 

If you can answer these questions (happy googling) then you will have the answer to your own question. Ask specifics if you are having any difficulties.

[Ophiolite]

You are, I think, still somewhat confused.

 

There is no caldera. A caldera forms when a magma chamber, emptied of magma, collapses. There is no connection between an inpact crater and a volcanic crater. (No nitpicking from others please.)

 

The depression you refer to is there. It is most certainly a physical remnant, though it has been subsequently buried by later sediments. You could say that this a result of new crust forming, but that would not be the conventional way to describe it. There is a possible similar crater, much smaller, also discovered by geophysical methods in the North Sea.

[Light Storm]

There is no connection between an inpact crater and a volcanic crater. (No nitpicking from others please.)

 

/Agree

 

If a meteor is big enough, and hits the ground fast enough the ground can liquified into a molten state which would leave evidence similar to that as a volcano, but they are very different.

 

 

 

[Luna]

Just a couple of tidbits I've read. At the Yucatan (Chicxulub) Crater some of the samples providing evidence of an impact included shocked quartz, tektites, and a gravitational anomaly in the area. Visible outcrops of the impact include cenotes which outline the crater's original impact rim. Cenotes are the gradual dissolving of upper limestone layers overlying broken-up rocks, or breccia. So on the contrary of the crust being filled in, the outline of the crater is actually eroding.

 

 

[Chalky]

Bear in mind that the Yucutan Peninsula is a relatively tectonically stable area in CONTINENTAL crust. It is very hard to either create or destroy continental crust so plate tectonics is relatively unimportant in this case. (Oceanic crust is being continuously created at ocean ridges and destroyed at subduction zones, but the impact crater is not in oceanic crust). As large areas of the continents are old Precambrian shields (i.e. before 500 million years ago) and the Chicxulub meteorite is only 65 million years old, it's entirely plausible that the impact crater is still there.

 

The reason we don't see our planet littered with craters (like the moon) is the active sedimentary cycle, which will erode the rim of the crater and infill the hollow with sediment. This will remove any evidence of the crater being seen from the surface. However, the different densities of sediments vs crust mean that the crater will show up on gravity surveys.

[Luna]

Very true.

 

It might help if you read up on the details of plate tectonics a bit more.