Science 3: The Rock Cycle

Today's lesson is on the rock cycle. Spoiler alert: it's way less effective at getting you to school than a bicycle. There's a reason wheels are made of rubber.

3rd GradeScience
LanguageEnglish Language

Transcript

00:31

be classified into three different types:

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Igneous, metamorphic, and sedimentary – and all three have their own specific properties, as well as uses.

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Igneous rocks are rocks that were once, well, not so rocky.

00:43

Kind of like music, before Elvis hit the scene. [Elvis singing on stage]

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But back to the rocks…what we mean by "not so rocky" is that igneous rocks weren't always rocks.

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They actually start as liquefied rock, bubbling deep down below the surface of the planet, [Lava bubbling]

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where they're melted by the Earth's core.

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Once the molten rock comes up to the surface and gets some fresh air, it rapidly cools off. [Molten rock appears from mountain]

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And when it does, it turns back into solid rock.

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Examples of igneous rock include granite, basalt and obsidian.

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And igneous rocks tend to be pretty darn cool looking, which is why they're often used by [Kitchen appears]

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interior designers to make things like countertops, backsplashes, sinks, floors, and tabletops.

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We heard some designers wanted to use them for mattresses…kinda glad that never caught on. [Girl sleeping on rock mattress]

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Next, we've got metamorphic rocks.

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These rocks are also created by heat, but they skipped that whole messy "liquefied" phase. [Coop discussing metamorphic rocks]

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When a rock is exposed to extreme heat – but not enough heat to straight-up melt it – it

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can still be affected by it, and transform into a new, metamorphic type of rock. [Rock goes into super heat machine]

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Kind of like when Pokémon evolve, but…way less interesting to watch.

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Because so much heat is needed to make them, metamorphic rocks are usually found below [Metamorphic rocks under earths surface]

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the earth's surface or near volcanoes. Examples include jade, marble and slate.

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Metamorphic rocks have been used in art, sculpture, and construction throughout the history of

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humanity – from the Ancient Greeks carving marble statues and columns to roofers using [Ancient greek statue appears]

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slate tiles today. Then we've got sedimentary rocks, which are

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formed on the surface of the earth when different rock sediments are fused together over time. [Dino discussing sedimentary rocks]

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Sedimentary rock is the most common type of rock to be found on the earth's surface, and

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include sandstone, amber, and limestone, which does not taste like limes…

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Trust us on this one. [Girl at restaurant table with menu]

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Since sedimentary rocks are so common and plentiful, we regularly use them in construction

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– if something is made from cement, sand, or gravel, well then it's made from sedimentary rocks.

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Take one look at a city and you're basically just looking at rearranged sedimentary rocks.

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And you thought we were long past the stone age. [Cave man in New York]

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Clearly, rocks are essential to human civilization – without them, we'd be living in, well, dirt.

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But rocks aren't exactly…perfect.

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One of its biggest drawbacks is that natural weather like wind and rain can take its toll [Rock in street being rained on]

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on rock, eventually eroding and weathering it.

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Buildings can erode...

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Ancient art can deteriorate...

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And even that gorgeous marble sink might eventually erode from use – though you might need to [Marble sink eroding from water]

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give it a few thousand years.

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But hey – considering the Earth so generously offered us all of this amazing rock for free,

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we probably shouldn't be complaining.