When it comes to measuring the movements of plate tectonics, how accurate are these measurements by using topography(on-site)? Did these measurements match satellite measurements?
Yes there is a “supercontinent cycle”. So they have formed, and then break apart again eventually. As I understand, it has to do with all the heat that builds up under the supercontinent and causes rifting.
It’s possible for the different boundaries to be subducted under a continent (like in this case, under North America. But things get warmer in the mantle, so the processes are different, so even if there is still motion apart or together it doesn’t make new sea floor, or volcanoes, etc.
Yes, the other Hawai islands do not have active volcanoes. The eruptions just stop happening… and there is actually a new island forming by volcanic eruption off the coast of the big island!
To become “inactive” it just means the eruptions stop. So erosion and weathering take over. The rocks cool down (become more dense), so there is some elevation loss due to isostatic effect also. Eventually they become dense and eroded to the point they sink below sea level.
Subduction tends to happen when the sea floor is old and dense. The Atlantic sea floor isn’t super old… but also it is difficult to get subduction started. You have to overcome some resistance to get the process going. It’s a big question in geology, how that can happen.
The continents form by many different processes, so they are more diverse. Usually at least though there is the old granites and gneisses and other “hard” rock. Then often one or more layers of sediment on top. The continents are many times older than the sea floor, so they have a more complicated history and structure.
Yes, the India-Asia collision will eventually stop. (Today we live in New York at the site of an old collision much like that one). And the placement of the continents keeps shifting, so yes, over time the arrangement will be quite different…
