Audio Transcript Auto-generated
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Hey, guys, Welcome back.
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We're gonna do see for spreading part two here.
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So we got through about half of the presentation yesterday.
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I'm hoping we'll get through the rest of the power
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point today.
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Remember? I do want you to download that power point,
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um, posted in school g That way you could actually
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run the power point and see some of the videos
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that air in there.
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So yesterday you had one video will just be for,
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um that's what we got built with Bill Nye explaining
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sea floor spreading to you on dhe today.
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You're gonna have a few more videos when we're talking
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about magnetic reversals and things like that.
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Okay, so please make sure you're downloading that power point.
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And you can even pause this video while you watch
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those power points and you can come back and then
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continue the lecture.
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Okay, so let's go.
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Let's continue with sea floor spreading.
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Okay, So see for spreading part two.
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Here we go.
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Okay. So look at this picture.
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This is a review of what we talked about yesterday.
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How we have that mantle and how that conviction current
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underneath is gonna have that magma come up.
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And then that knew that Lava is going to make
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that Newcrest for us.
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And because of its gonna keep moving and pushing out,
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that new crust is going to keep being made.
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Okay. And so we're gonna go on today.
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We're going to talk.
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Whoa! I don't know why this is moving.
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Let me see if I can get there we go.
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All right.
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So what we're gonna talk about today is what's gonna
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happen to that crust?
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So there was a question that was coming about one,
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and Harry has thought to consider it was Why isn't
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our world getting bigger and bigger and bigger and bigger
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and bigger?
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Well, because something's happening.
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It's called subduction, and subduction is what's going to happen
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to our crust.
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It's gonna go back under and go back into the
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mantle. So that's what we're going to talk about today,
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with some more of sea floor spreading.
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Alright, So here's that process of sea floor spreading.
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I do want you to know this process.
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Okay, So remember it began to the mid Ocean Ridge,
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which is on that oceanic, Um, that that that mid
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ocean ridge, that oceanic crust okay and then that that
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magma is gonna come from several kilometers below the surface
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and it's gonna erupt.
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And when it erupts, that's lava.
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And then those older rocks on the both sides of
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the rich they're gonna move out because that new crust
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is being made.
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Okay. And so we're gonna have that new strip of
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rock in the center, and then all the old stuff
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is gonna move away and make room for the new
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stuff. All right, so there's another picture to show you
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make sure you get that in mind how all of
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that works.
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All right, so now we're gonna talk about the evidence
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for sea floor spreading.
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What did the what Harry has used.
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So they got evidence from multi material.
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They got evidence from magnetic, strict strips, Okay.
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And they got evidence from drilling samples.
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And this was what brought Alfred beginners theory back to
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life. This is what brought back everybody to say.
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Hey, Harry has brought forward this information.
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Maybe we should take a look.
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A continental drift again.
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Okay, So here's a video.
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This is gonna be about sea floor spreading and how
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it moves about so you can go ahead and pause
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right here.
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And you can watch this video in your power point.
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It's gonna explain how sea floor spreading works, and you're
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gonna see that movement.
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Okay, so you're gonna see this movement here.
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You're going to see how this is gonna come out.
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It's gonna push and push these things to the side.
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Okay? So it's gonna push it away, and you're gonna
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have this magma coming out of this mid ocean ridges
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gonna push out.
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It's gonna make new material here.
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New crust.
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It's gonna push the older stuff this way.
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Okay, so that's to give you a visual of, um,
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sea floor spreading.
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So again, you can go ahead and posit here and
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watch that video in your power point.
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All right, so now let's talk about deep ocean trenches.
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Okay? So when Harry has talked about sea floor spreading,
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he, um, said the words not getting bigger and bigger
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and bigger that that there has to be something else
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that's going on.
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So he says this is not getting bigger.
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This has to be going under somewhere else.
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The crust has to be being destroyed here.
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So this is what we're talking about here.
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is called deep ocean trenches.
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This is where the oceanic crust is gonna subduction.
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It's called subduction.
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Subduction means to go below.
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It's going to sub stuck below the continental crust, and
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it's gonna go back into the mantle like it's being
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recycled. Okay, so that's what this is.
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That's what's gonna be happening here at these deep ocean
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trenches. So hint, hint.
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This is where the oceanic crust is gonna bend.
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Go back underneath and it's gonna be recycled into the
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mantle. Okay.
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And this process is called subduction, so hint, hint.
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I want you to know this word.
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Subduction. So this is that process where that ocean floor,
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because of sea floor spreading, it's going to be moving.
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Well, it's gonna have to go back underneath, okay?
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And this is what subduction is that that ocean floor
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is going to sink beneath and go back into the
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mantle and they take place at trenches, Hint, hint.
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They take place at trenches.
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Okay, so this is part of the process of C
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four spreading okay.
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And so that lava is going to come out and
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it's gonna form that the lava is gonna come out.
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It's gonna form that new crust it's going to move
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across. Members had a divergent boundary into the mid ocean
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ridge that crosses and come out.
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It's gonna move and it's gonna get to that trench.
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And once it reaches that trench, it's gonna subduction and
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go back into the mantle.
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Okay, so that is how sea floor spreading works.
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It's all part of that process.
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Okay, so here's some of the words I want you
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to remember.
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This is what we was in the beginning of the
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vocabulary where Ridge push is when it's the weight of
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the uplifted ridge that pushes the oceanic plate.
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Or that that the oceanic plate towards the trench.
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So the ridge push is that, um, the weight is
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pushing that ridge.
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It's pushing that crust to the to the trench to
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that subduction zone in that trench.
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Okay, so that it's pushing Ridge push.
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That weight is pushing the crust to that trench so
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it can be subduction.
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Okay, And slap pull is where the weight of that
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sub ducting pulls out.
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Lift this fear into the subduction zone, so it's gonna
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pull it so that weight of that plate that's going
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under is going to pull its gonna pull it under
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back into the mantle.
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Back into that lit the sphere.
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Okay, remember the lift this fear was belittle?
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This fear was the crust and the upper part of
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the man's Okay, so that is going to be pulled
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in. That is what is gonna be referred to as
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the slab pull.
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Okay, make sure you know those two.
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All right, so here is some pictures to see it.
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You can see how it's working here.
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So you see how you have that conviction current underneath
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That's gonna help those, um, that magma to keep rising
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up. But it's also going to kind of help to
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move that oceanic crust.
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And that weight is being pushed towards the seduction zone.
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That's the ridge push.
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Okay. And then when it's going underneath, it's gonna sink
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underneath that continent at that trench, it's being pulled under.
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That's the slab pull.
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So make sure you know the difference between the rich
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push and the slab pull.
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Please make sure you know the difference between the two.
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Alrighty. Okay, So you're gonna have another video here to
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explain. Rege rege pushing slab pull.
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So what you can do here again you can also
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posit right now and watch this in your power point.
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Okay? So you're more than welcome to pause this right
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now and watching your power point and come back and
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resume your, um, power point or this this presentation.
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Alright, going on.
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So here's another video you're seeing of how subduction occurs.
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This will be in your power point.
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Okay? So go ahead and pause again and watch this
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video of how subduction occurs in this video.
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You're going to see how that crust is going back
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into the mantle.
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How there is that slab pull.
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It's being pulled and that going back into the mantle
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and essentially being recycled into the mantle.
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Okay. And here's another one.
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Another video showing you seduction.
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So I'm showing you these videos because I do want
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you to know this this process of subduction.
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So go ahead and pause this presentation again and go
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ahead and watch this video of subduction.
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Alright, So here's the Here's the visualization of the mid
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ocean ridge with subduction.
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So this middle part right in here in that light
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blue part you see how it says Mid Ocean Ridge.
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That's where that new crust is gonna be made, it's
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gonna be made, and it's gonna be pushed outwards.
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Okay, so that new crust is gonna be made, it's
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going to come out, and it's gonna push outwards, okay?
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And this is going to keep going.
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It's gonna keep going till it hits a trench and
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want to hit that trench.
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It's gonna go back under into the mantle.
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Okay, so it's gonna push out, and you can see
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this right here.
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You can see where subduction occurs.
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So I know this is kind of hard to visualize
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the sea floor spreading, but we are going to do
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a lab tomorrow to visualize and see how it works.
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Okay, So remember, for that lab, you're gonna need two
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pieces of paper, um, scissors and at least two crayons
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or two colored pencils or two markers of different colors.
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Okay, if you don't have those, remember, though, let me
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know as soon as possible so I could get that
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to you guys and have them in the office ready
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for you.
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So here are some of the information here of the
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evidence that the scientists collected.
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So scientists collected samples of deep sea sediments and the
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crust, and they made two big discoveries.
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They found out that rocks that make up the sea
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floor, they vary in their ages.
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They vary in their ages in different places.
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So rocks near the ocean ridge were younger and rocks
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near the trench were older.
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So the oldest part of the ocean that they found
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so far is 180 million years old.
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But that's really young.
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Come in geology terms because we have continental rocks that
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are three point eight billion years old.
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And remember when we first started talking about this last
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yesterday, people thought that the ocean floor never changed and
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that it was the oldest part.
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But when they looked at the ages, the ocean the
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oldest part there's one stuff that's 801 180 million years
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old. But we have Continental rocks over here, 3.8 billion
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years old.
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Why was there that different?
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Because the younger rocks or by the mid ocean ridge
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and they're pushed out to the right.
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They're pushed out to the right, and then they're gonna
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be the older stuff's gonna be by the trench.
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Okay, so these sediments were deposited on the ocean floor
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and the thicker sediments were away from the Ocean ridge
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because of how it's moving.
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It's kind of building up there.
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So that's what they discovered with these ocean rocks and
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these sediments.
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All right, so they also got some evidence from drilling
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samples. So some of the samples on the sea floor
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they were drilled and they were studied, and some of
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them showed that the where the oldest rocks were.
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So again the oldest rocks were near the trench, and
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the the younger rocks were near that mid ocean ridge,
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which showed sea floor spreading, was occurring.
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There are rocks that are younger, and there are rocks
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that are older, and it is proving this theory or
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this Ah, this theory of sea floor spreading.
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Okay. And then they found this also this multi material.
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They found that new material that that that magma, that
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lava erupting at the mid ocean ridges and when it
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was hardening because remember, under the water, it's cool, it's
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gonna harden, and it's going to make that new crust,
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and eventually it's going to keep erupting and push it
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out. That was the evidence of the molten material.
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Okay. And so here we go, we're gonna talk about
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magnetism and where we're gonna end off today.
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Okay, so let's start off.
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Let's start off with paleo magnetism.
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That's the study of magnetic record.
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And that's what we're gonna talk about here.
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We'll probably finish this on Thursday.
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Okay, so, um, basalt is rich in iron, and it
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gives an accurate record of magnetism.
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Okay, so that basaltic lava, it's gonna cool.
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It's gonna have all the iron in it, which is
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going to give us that magnetic fields going on.
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And that's what we're going to use with those Magnum,
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Magnum Etame.
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I cannot say those words.
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Okay, but the magnet magnetometer, there we go.
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Could not say it.
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So they're going to give us the how the Earth's
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magnetic field is at the time.
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I'm tired at the end of the day, guys.
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I'm trying to record this for you guys.
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Sorry. I'm tired trying to speak, okay?
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And we're gonna have evidence of magnetic strips, okay?
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And so these are gonna show patterns on the rocks
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of the ocean floor.
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So it's gonna show stripes.
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We can't see them, but with the magnet, they can
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actually detect that.
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The magnetism of it, okay.
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And so we're gonna go into something called magnetic reversal.
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That's when the Earth's feel is gonna change the earth's
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magnetic fields.
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Gonna flip.
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So, like, right now, we are in a magnetic pull
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north will eventually.
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After millions of years, it's eventually going to switch back
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to south.
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And there are stripes in the ocean floor that are
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showing this magnetic memory.
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They're showing that this has happened before in the past.
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Okay, so you're gonna see here.
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Here's that picture.
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It's showing you what it looks like, and it's gonna
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flip on this magnetic reversal here, and it takes time.
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It's gonna move, and we're gonna see this magnetic stuff
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happen over time.
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And you're gonna see these magnetic stripes.
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So as we go on, there's gonna be more videos
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to explain this to you in here.
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Okay, so that's where we're gonna end right now.
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And you can keep going on and look at the
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videos will end there and I'll finish the video.
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Thio, make the rest of the power point.
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All right, So you guys have a