Lizzie Borden Society Forum

There is a new series on History Channel- How The Earth Was Made.

I wanted to see the Mariana Trench and that was on 2 nights ago.
Did anyone watch it, and can you explain something I may have missed?
I may have to watch it again to get it all.

(Please reply only if you actually watched it, OK? Thanks!)

Well, it's sure to repeat, so if you catch it, I want to understand about the subduction. They didn't seem to be clear on it and one expert, the lady, made no sense to me. It was like being hypnotized by her explanation, and then waking to realize I had not understood plain english!

Here is a site describing subduction. But I think the graphics in the TV show, paired with the scripted text was not understandable- the part that shows the relationship between the trench and the volcano forming.
I'd like to know if it was me, or the writing.

If you see the show- let me know! Thanks!

http://library.thinkquest.org/17457/pla ... nics/5.php

It is one crustal plate meeting another plate and descending beneath it. Geologists tend to become confusing with their fancy talk to a point where they are not understandable to the layman.

A simple experiment: Place your two hands next to each ohter and slide eone beneath the other. That's an example of the process of subduction.

William, Loved you explanation, it was short & concise, most of all I understood it!!!!

Thanks William! I forgot you are a geologist!

It's understandable, the way you describe subduction, I agree.

But the part I didn't get was how they kept showing the graphic of the trench and a quick travel view over the earth to the volcanos being formed and the relationship between those- that's the part that didn't make sense, in the words they used to describe it.

The volcanoes they were describing were part of a weakness in the Earth's crust known as a mid-ocean ridge. The formation of these ridges causes the plates to move away from the ridge as the volcanoes erupt and push the plates opposite directions. Are those the volcanoes you were referring to?

Maybe. When you say push the plates in opposite directions, do you mean they go off in opposite directions, or opposite to the site and toward the area of weakness that is the subduction zone?

Then, if that is half of the planet's surface activity, what is happening opposite to that on the other side of the planet? Does that seem like a reasonable question?

The oceanic ridge forms in a linear fashion, so imagine north-south orientation. This formation pushes two separate plates, one east and one west. These are subducted beneath a continental plate, which is thicker and/or denser than the oceanic plate.

If we can imagine half the planet's surface taken up by a single oceanic ridge propelling two plates opposite directions, then the other half would be a single continental plate. That's a perfectly reasonable question and allows a (hopefully) clear explanation.