- Explore_ The Moving Earth (2023)

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Harvard University *

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180

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Geology

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Oct 30, 2023

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Uploaded by AmbassadorGiraffeMaster852

The Moving Earth At this point we know a few things about our planet. We know that the Earth is heterogeneous, meaning it is made of di±erent materials. We know the planet consists of layers: the core, mantle, and crust. We know that the Earth’s crust is made of plates, called tectonic plates, that are moving on top of the mantle; the magnetic stripes on the seaﬂoor provide evidence to support this claim. But what is the mechanism that drives this movement? What actually causes the tectonic plates to move? To help you answer that question, you’ll be exploring the following experimental setup and watching it in action: Materials: ● Glycerin in a petri dish ● Candle ● Ring Stand ● Wood Splint ● Matches Procedure: 1. Place your petri dish on top of the ring stand, with your candle underneath the center of the petri dish. 2. Fill the petri dish to a depth of about 1 cm of glycerin 3. Cut or break your wood splint in half, and place the halves side by side, centered over where the ﬂame of the candle will be. Top view Side view Based on what you already know, what do you think will happen to the wood splints after the candle is lit? It burns Perform the lab/watch THIS VIDEO and observe what happens. Describe what you see below. It moves Now it’s time to draw and explain what happened. Click edit on each picture and using arrows and text boxes, add the following information to the original picture: *add arrows to show the movement of the particles of the glycerin *add another set of arrows to show the movement of the wood splints *add labels to describe what is happening and why

In the space below, explain why the movement is happening. Be sure to include what types of heat transport occur (there are at least two), how the density of the glycerine changes, and how this causes the movement. Convection and conduction What does this activity model for the Earth system? (Hint: the wood splints represent the ocean ﬂoor near a mid-ocean ridge). This ocean ﬂoor moving What part(s) of the glycerin/wood splint model represent each of the following parts of the Earth system? If the part is not represented in the model, write “not represented”. Part of the Earth Model Oceanic plates Wooden splints Mid-ocean ridge Between the wood splints Mantle liquid Continental Plates none Liquid Outer Core candle Radioactive elements wax What would happen to the movement of Earth’s tectonic plates if there was no “candle”? Explicitly state what the candle represents in this model as a part of your answer to this question. It would have no outer core What limitations does this model have on explaining how and why the ocean ﬂoor spreads? (for example: Do the states of matter for each component match? What does the movement NOT show? Does it model the “formation” and/or the “destruction” of ocean ﬂoor?, etc…) Mid ocean ridge

Read the following two paragraphs to help you answer the questions that follow, and to be able to use more scientific language in your descriptions. Movement of Plates: Basalt vs Granite, divergent vs convergent A more technical way to describe two pieces of ocean ﬂoor moving apart from each other is to say that “the two tectonic plates diverge”. What is a tectonic plate? What does it mean for two plates to diverge? (Hint: your wood splints diverged from one another) Areas on the earth where two plates move away from each other are called divergent plate boundaries. Since the earth is finite (that is to say it is not growing), if two plates are moving toward one another, we say that these two plates converge . These areas of the earth are called convergent plate boundaries. Common places on the earth where we see convergent plate boundaries are where oceanic crust meets continental crust. But what happens when these two types of crust meet and “crash into each other”? (okay, crash is an overreach, they do push against one another with tremendous force!) After reading the two paragraphs above, give your best definition of each term below: Term Definition Diverge Areas on the earth where two plates move away from each other Converge If two plates are moving toward one another Plate boundary Common places on the earth where we see convergent plate boundaries and where oceanic crust meant continental crust Tectonic plate Areas on the earth where two plates move away Observe the rock samples below: Granite Basalt Density: 2.75 g/cm 3 Density: 2.9 g/cm 3 Location: Continental crust Location: Oceanic crust

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Imagine that the basalt and the granite begin pushing into each other at a convergent plate boundary. One of these materials will rise (and often buckle under the tremendous forces involved) and the other will sink, or subduct under the other material. Which type of rock would you expect to subduct ? Explain your reasoning. You should use at least the following pieces of evidence to support your answer: (a) the relative densities of each rock, (b) what you know about the age of the ocean ﬂoor compared to the age of the continents, and (c) the movement of the ocean ﬂoor itself. The basalt is gonna sink because its more dense The material that subducts doesn’t disappear from the universe. Where does it go? Under the water Watch this short animation showing a subduction zone , then describe three things that can happen to a subducting plate after it subducts: 1 It sinks 2 The plate has a specif movement 3 The water current is going down Putting it Together Using the knowledge gained from last week’s Earth’s Interior Heating Sources article and today’s activity, in your own words explain what causes the tectonic plates to move. Be sure to include terms such as mid-ocean ridge, magma, convection, seaﬂoor spreading, heat transport, mantle. In places where convection currents rise up towards the crust's surface, tectonic plates move away from each other in a process known as seaﬂoor spreading

Earth’s Layers Model It’s time to return with your Layers of the Earth model and add this new information. Add the following to your group and personal model: *divergent plate boundary *convergent plate boundary *mid-ocean ridge *subduction *convection *basalt *granite *arrows showing the movement of the tectonic plates, both oceanic and continental crust *arrows showing the movement of the mantle