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If you know the age of different islands, how do you find where the tectonic plates are moving? I thought they would move toward the younger plates but in the test I was looking through it said it moved toward the older islands.

freed2003 wrote:If you know the age of different islands, how do you find where the tectonic plates are moving? I thought they would move toward the younger plates but in the test I was looking through it said it moved toward the older islands.

The direction of plate movement would be whatever direction the tail of the island chain points to (if you're talking about hotspot islands). The hotspot is stationary and the plate moves, so the youngest island would be closest to the hotspot and the oldest island would be furthest. That means that the direction of plate movement would be in the direction of the older islands. It's kind of hard to explain (or maybe I'm just bad at explaining...). Look up a map of the Hawaii island chain's movement if this is isn't helpful lol.

An analogy I use is a conveyor belt making...candies or something. The oldest ones are further along the belt; the youngest ones were just spat out of the machine! I find myself misreading my hot spot map occasionally because I do think it's not totally intuitive (which, by the way, if you don't have that map yet, you can find it in that book I was raving about a page or two back...haven't found anything better).

I searched the web for like 2 hours, and I found information on intermontane basins. Can someone plz tell me what they are?

I found no* information on it. XD

tyasasvi wrote:I searched the web for like 2 hours, and I found no information on intermontane basins. Can someone plz tell me what they are?

Intermontane basins form between two mountain ranges as a result of the stretching, and usually subsequent graben formation, of the land in between, with a filling-in of sediment. For example, the Basin and Range in the western US constitutes a series of parallel mountain ridges/ranges and depressions, formed by alternating horst/graben sequences or a series of tilted half-graben (varies based on the particular location) with the depressions filled with sediment. Each of these depressions would be an intermontane basin. The term is a sort of catch-all term for "other" basins.

driedmango wrote:

freed2003 wrote:Could someone give me an example of a question about glaciers? Because all I have on my notes are land forms made of glaciers

I haven't seen many glaciers questions at all on tests this year. I think tectonics focuses more on plate movement and mechanisms that drive it and stuff. The only thing you might see about glaciers on a test would probably be isostasy related (ex. what is it called when land originally covered by glaciers rises to its original elevation after the glaciers retreat?).

A clear example of this is seen in the Alps. Glacial isostatic uplift is due to the loss of continental ice sheets.

Why does the left most strip have normal polarity?
Also how can you draw magnetic striiping>(use dark for normal polarity)

freed2003 wrote: Why does the left most strip have normal polarity?
Also how can you draw magnetic striiping>(use dark for normal polarity)

As new magma comes up at the mid-ocean ridge and cools, it records magnetic north, creating stripes of normal/reversed polarities that are mirror images on either side of the ridge. When you're talking about the left-most strip, I'm assuming you mean the stripe of light orange. So that strip would have a normal polarity because when that magma was cooling, earth's magnetic north was the same as it is currently (and it also matches the strip of normal polarity on the right side).

To draw the pattern of reversals, you might want to do something like this:

At an invitational earlier this year, I received this question:

The mantle's transition zone is characterized by an abundance of what compound?

And the answer was "hydroxide".

Can anybody explain why? I can't find any information on the internet about this.