A new friend Savannah and Sam learn about different kinds of igneous rocks, which form after liquid magma or lava cools into solid rock.
Teachers and parents: scroll down to check out the Next Generation Science Standards (NGSS) for this episode!
Hosted by: Savannah Geary (they/them)
NGSS Disciplinary Core Ideas
PS1.A: Structure and Properties of Matter
Different kinds of matter exist and many of them can be either solid or liquid, depending on temperature. Matter can be described and classified by its observable properties. (2-PS1-1)
Different properties are suited to different purposes. (2-PS1-2),(2-PS1-3)
Join Jessi, Squeaks the Robot Lab Rat, and all their friends at the Fort as they conduct experiments, research new questions, and talk with experts to learn about the science-filled world around us.
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SciShow Kids is ideal for early-elementary learners, Grades 1-3, and many episodes are structured around the Next Generation Science Standards (NGSS) curriculum.
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Whoa, that one is really cool! Yeah. Hi! My name is Savannah. I’m
a friend of Jessi’s from work. I’m visiting the Fort and Sam has been showing me some great photos of the moon. Yeah! I wanted to get a better look at
all those dark spots covering the surface.
00:23:
I was doing some reading
about them, and it turns out those spots are actually
special rocks called basalt. A long time ago, lots of places on the
Moon got flooded with lava from volcanoes, and the lava somehow turned into rocks. That is so cool!
01:38:
I didn’t know that spots on the
Moon were made from igneous rocks! Ig-na-what-now rocks? Oh, igneous rocks are a special type of stone. They form when a bunch of super hot liquid rocks cool down and hardens into
brand new solid chunks of rock.
01:55:
You said that parts of the Moon’s
surface got flooded by lava, right? Uh-huh. Well, volcano lava, which is called
magma when it’s still underground, is really just a bunch of rocks that
got so hot, they melted into a liquid. Like when an ice cube gets
warm enough to melt into water!
01:12:
Exactly! And when the fiery hot
lava or magma cools back down, they go from being liquid
rock, to solid igneous rocks. The word igneous even comes from the
Latin word ignis, which means fire! That’s how I remember that igneous rocks are made from fiery heat, then cooling back down.
02:33:
So igneous rocks are just rocks that
have changed from being liquid to solid? Yup. But if those igneous rocks melt
again, they won’t go back to being the same exact rock they were
before they melted the first time. Because the ingredients in the lava might
be slightly off, or the amount of heat
02:52:
or pressure in the environment around
the liquid might be a little different. You might even wind up creating another
type of igneous rock, completely! I’d say that’s cool, but I
wouldn’t want you to groan. I kinda wanna groan anyway.
02:07:
You can find basalt on both the Moon
and the Earth, and in both places, it’s made from lava that cools
after it erupts from a volcano. But there are lots of other
igneous rocks that do that, too. Together, they’re called extrusive
or volcanic igneous rocks.
02:24:
And there are also igneous rocks that form
without getting shot out of a volcano. Instead, they’re made when magma
cools and hardens underground. Those are called intrusive
or plutonic igneous rocks. So basalt is an extrusive igneous rock, because it cooled and hardened above the ground.
03:42:
This is a really interesting way to sort rocks, but what if I don’t know where a
rock came from, or how it was formed? How can I tell if it’s an igneous rock,
or if it’s an extrusive or intrusive? That’s a really good question!
03:55:
We usually aren’t able to watch rocks
form, so we have to look at what we can see and observe certain properties
about the rock to make our guess. The properties of an object can include
how it looks, feels, or even tastes.
03:09:
But when we’re dealing with rocks, we
don’t really need to think about taste. Yeah I don’t really think I want to lick a rock. Extrusive igneous rocks tend to form a lot more quickly than intrusive igneous rocks. And that means the two often look very different.
03:24:
Because they cooled and solidified
super fast, extrusive igneous rocks might look grainy or glassy
because the crystals are too small to see with your eyes. Or they might have bubbles of
air that got trapped inside them! Check out this pumice stone. Whoa, I can see the air bubbles!
04:46:
And it’s really light for a rock. That must be because of all the
air caught inside of those bubbles! So pumice must be an extrusive igneous rock! You got it. Now let’s compare that
pumice to this piece of granite. Oh wow, the bits and pieces
in this rock are much bigger,
04:03:
I can see all of the little
crystals that make up the rock. Yeah. Can you think of why they might be so big? Is it because they had more time to grow? The liquid rock took a lot of
time to cool down and harden? I think you’re on the right
track, there…Keep going, Sam. What else do you observe?
04:19:
I don’t see any air bubbles! So this rock must have been formed underground, where the air couldn’t get caught inside. So…granite is an intrusive igneous rock? Yes. Granite is super useful, too! What other properties can you notice
about granite when you hold it?
05:35:
Well it’s not a very big
piece, but it’s pretty heavy. And it feels pretty hard. Exactly. And because of all that,
some humans use granite to make really strong surfaces that get
used a bunch, like countertops. Plus, because of the way it formed,
granite doesn’t react that much to heat.
05:54:
So it’s especially good for kitchen countertops, where you’ll find people using a lot
of hot pots and pans over the years. I don’t think an extrusive
igneous rock like pumice would be very good for that.
It doesn’t seem as strong.
05:07:
True, but all of the air bubbles in
pumice give it a very interesting texture. Yeah it’s super rough. Is
texture another type of property? It is! Pumice might not be as strong as
an extrusive igneous rock like granite,
05:21:
but its rough texture makes it great to put
in scrubbers that clean or polish things. And some people even use pumice to
scrub old skin cells off their body! And because pumice is so light,
it can be added to things like concrete to make it strong, but not as heavy.
06:38:
Wow, it sounds like igneous
rocks have lots of cool uses! It’s amazing that liquid magma and lava
can become rocks that we use every day. And the more we learn about rocks, the more interesting ways we
find to sort them and use them!
06:52:
Say, we might not be able to visit
the igneous rocks on the Moon, but there are amazing places all over the world where we can see different kinds of igneous rocks. We could visit the Giant’s
Causeway in Northern Ireland, which just like those dark spots on
the Moon is made up of basalt rocks.
06:10:
Or, we could go to Bear Lodge, also known as Devils Tower National Monument, in Wyoming. There’s a huge, natural
landmark over there made of a rare igneous rock called phonolite porphyry. Sounds like we have some traveling to plan! I’ll get my notebook, and we can start writing out
06:27:
details for some trips we’d like to go on. You can learn about igneous rocks around
the world, or in your neighborhood. Do you have any igneous rocks around you? Do you think that they’re intrusive, or extrusive? And remember, if you want to
keep exploring different rocks,
07:41:
and lots of other fun science
things, we have lots of other SciShow Kids videos to help you learn more. We’ll see you next time, here at the Fort. Bye!