Teachers and parents: scroll down to check out the Next Generation Science Standards (NGSS) for this episode!
Savannah and Sam take an adventure through the world of rocks!
Hosted by: Jessi Knudsen Castañeda (she/her/they/them)
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From the team behind the YouTube series SciShow comes SciShow Kids!
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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Original Episodes:
https://youtu.be/_ebd7k_lUAs
https://youtu.be/b5eGg3TxIKc
https://youtu.be/8ZT9Bt7VZDU
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wow that one is really cool yeah hi uh my name is Savannah I'm a friend of Jesse'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 I was doing some
00:23:reading about them and it turns out those spots are actually special rocks called Basalt a long time ago lots of of places on the moon got flooded with lava from volcanoes and the lava somehow turned into rocks that is so cool I didn't know that spots on the moon were
01:39:made from ous rocks IGN what now rocks oh ous rocks are a special type of stone they form when a bunch of super hot liquid rocks cool down and Harden into brand new solid chunks of rock you said that parts of the moon's surface got flooded by lava right mhm well Volcan
01:00: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 exactly and when the fiery hot lava or magma cools back down they go from being
01:19:liquid rock to solid ous rocks the word ous even comes from the Latin word ignis which means fire that's how I remember that Ignus rocks are made from fiery heat then cooling back down so ous rocks are just rocks that have changed from being liquid to solid yep but if those
02:38:ous 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 or pressure in the environment around the liquid might be a little different you might even wind up
02:57:creating another type of ous rock completely I'd say that's cool but I wouldn't want you to groan I kind of want to groan anyway 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
02:16:there are lots of other ous rocks that do that too together they're called extrusive or volcanic ous rocks and there are also ous 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 ous rocks so
03:37:Basalt is an extrusive ous rock because it cooled and hardened above the ground 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 was an ous rock or if it's extrusive or intrusive that is a
03:53:really good question 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 but when we're dealing with
03:10:rocks we don't really need to think about taste yeah I don't really think I want to lick a rock extrusive ous rocks tend to form a lot more quickly than intrusive ous rocks and that means the two often look very different because they cooled and solidified super fast
03:27:extrusive ous 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 pmus Stone whoa I can see the air bubbles and it's really light for a rock that must be because of all the air
04:49:caught inside those bubbles so pmus must be an extrusive ous rock you got it now let's compare that pmus to this piece of granite oh wow the bits and pieces in this rock are much bigger I can see all the little crystals that make up the rock yeah can you think of why they
04:07: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 keep going Sam what else do You observe I don't see any air bubbles so this rock must have been formed underground where
04:23:the air couldn't get caught inside so Granite is an intrusive ous rock yes Granite is super useful too what other properties can you notice about Granite when you hold it well it's not a very big piece but it's pretty heavy and it feels pretty hard exactly and because of
05:42:all of 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 so it's especially good for kitchen countertops where you'll find people using a lot of
05:59:hot pots and pans over the years I don't think an extrusive ous rock like pmus would be very good for that it doesn't seem as strong true but all of the air bubbles in pmus give it a very interesting texture yeah it's super rough is texture another type of property it is pmus might not be as
05:18:strong as an extrusive ous rock like Granite but its rough texture makes it great to put in scrubbers that clean or polish things and some people even use pmus to scrub old skin cells off their body and because pmus is so light it can be added to things like concrete to make
06:36:it strong but not as heavy wow it sounds like ous 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 see we might not be
06:53:able to visit the ous rocks on the moon but there are amazing places all over the world where we can see different kinds of ous rocks we could visit the Giants Causeway in Northern Ireland which just like those dark spots on the moon is made up of basalt rocks or we
06:11:could go to Bear Lodge also known as Devil's Tower National Monument in Wyoming there's a huge natural Landmark over there made of a rare ous rock called phonolite poery sounds like we have some traveling the plan I'll get my notebook and we can start writing out
06:27:details for some trips we'd like to go on wow check this one out Savannah H sometimes it's hard to pick my favorite oh hi everyone Sam and I are sorting his rock collection Savannah is Jesse's friend who knows a ton about rocks last time they were telling me all about
07:43:ignas rocks and now I want to know how many of them I have H what do you think about this one I got it from my parents cave I think that is a piece of limestone wait Limestone if I lick it will it taste sour well you probably don't want to lick anything that's been
07:59:on the ground Sam but even if it were clean no it wouldn't taste like lime it's not named after the fruit it just happens to have a name that sounds the same well that's confusing is limestone an Ignus Rock no Limestone belongs to another large group of rocks called
07:18:sedimentary rocks and just like the name Ignus helped us understand how ignas rocks form the name sedimentary tells us how sedimentary rocks are made sediments are little little pieces of material that have settled onto the bottom of a liquid but it doesn't matter how big
08:35:that liquid is it could be as big as an Ocean or as small as this glass so like when I finish my drink of hot cocoa and I find a bunch of brown clumps have built up in a ring around the bottom of the cup yeah those clumps are sediment but when we're talking about rocks the sediment tends
08:54:to be small pieces of dirt or Pebbles or even bits of broken seashells m I wouldn't want to drink those but how do they get into the water in the first place well it can happen a bunch of ways but one of the most common is called erosion which is also sometimes called
08:10:weathering because it can be done by wind and running water basically over really long periods of time wind and water will flow over the surfaces of rocks and slowly break off tiny pieces and carry them away the original Rock maybe one of those ous rocks we learned
08:28:about last time will get smaller and its surface will get smoother over time but all the pieces that are carried away have to go somewhere they might wind up at the end of a river spilling into a calmer body of water like a lake so over time you can get a bunch of different
09:46:sediment layers that grow on top of one another and after an even longer time these layers get pressed together into a sedimentary rock but remember sediment isn't just tiny bits of rock so times the layers inside a sedimentary rock can be made from things that were once alive
09:05:like plants or shells so what you're saying is that sedimentary rocks are kind of like Rock recycling kind of yeah and depending on what materials make up the sediment and how all the pieces stick together scientists have come up with ways to sort sedimentary rocks oh I
09:22:love sorting rocks for example some sedimentary rocks are made by taking smaller rocks that were created by erosion and squeezing them together really tight until they fuse together the individual pieces are called clasps so the resulting rocks are called clastic sedimentary rocks sandstone is
10:41:one of the most common versions of that and it's exactly what it sounds like a rock made from Sand can you see all the layers of sand that were built up on top of one another waa what about my piece of limestone some kinds of limestone can be called chemical sedimentary rocks
10:59:they form what water does more than just break a rock into tiny pieces it actually dissolves the rock into particles that are too small to see but if that water ever evaporates like a big lake that slowly dries up and completely disappears it will leave sediment behind
10:16:that can turn into sedimentary rock you can test this out yourself by dissolving some table salt into a glass of water setting the glass on a table and waiting for the water to evaporate the salt will be left behind at the bottom in fact fact halight is basically table salt but
11:32:in sedimentary rock form wa that's so cool but some Limestone can also be sorted into a different group of sedimentary rocks called biological sedimentary rocks can you guess what that group is for well biology means the study of living things so biological sedimentary rocks are rocks made of
11:52:living things yes well they're made of pieces of living things at least they form when living things die get piled up and squeezed together in some Limestone you can see the actual chunks of sea shells that were left behind by the animals that grew them but there are
11:08:other examples of biological sedimentary rocks like coal because coal forms when swamp plants turn into rock after tens of millions of years that's a long time yeah some changes in nature happen very quickly While others can take a long time like that pmus we looked at last
11:27:time that was created super fast after it got shot out of a volcano up into the air but it takes a lot longer for individual pieces of sediment to come together and get compressed into a new rock look at this coal Sam can you see the layering it's a little hard because
12:44:the rock is so black but yeah Cole sh looks like well coal but how do you know that my limestone is really Limestone well I don't know for sure but lucky for us there's an experiment we can do to find out want to try it yeah absolutely okay if you want to do this at home as
12:01:well get a grownup to help you out first gather your materials before starting you'll need a clear glass cup some vinegar and any rocks you think might be Limestone they should all be small enough to put inside of the cup first place your rock in the bottom of the cup
12:16:and then gently pour some vinegar in what do you see who it's bubbling that's because all types of limestone are mostly made of a material called calcium carbonate and when calcium carbonate interacts with the acid inside vinegar a chemical reaction happens that
13:38:breaks down a little bit of The Rock and creates carbon dioxide gas that's the gas that's inside all those Tiny Bubbles and acid reacts with rock to make gas that's awesome does this happen with all sedimentary rocks no it only works with rocks made from the same material as
13:55:Limestone calcium carbonate so this can be a fun way to narrow down what rock you have so I got this Limestone from a cave are there other places where we can find Limestone and other sedimentary rocks great question sedimentary rocks exist all over the world for example the
13:13:pyramids of Egypt were partially constructed out of huge Limestone blocks and uaru in Australia is a giant piece of sandstone but one of my favorite examples of sedimentary rocks can be found near the town of punakaiki on the southwestern coast of New Zealand the
13:30:pancake rocks these rocks are made from alternating layers of limestone and siltstone which is another kind of sedimentary rock that's made from clay and mud they formed about 30 million years ago and were slowly pushed above the water Surface by a series of earthquakes then over thousands of years
14:49:a combination of blowing wind crashing waves and sprinkling rain eroded parts of each layer but the silt Stone was eroded more easily than the limone Stone so now the towers of rock look like stacks of limestone pancakes man looking at those rocks makes me hungry me too I
14:08:think it's time for a snack oh hey Sam have you finished sorting your rock collection yet yeah I'm taking a break from sorting but I don't want to put my rocks away yet they're just so pretty they sure are hi everyone I'm Jesse's friend Savannah and I've been working
14:24:with Sam on his rock collection and it's so much work well if you're feeling tired Sam maybe we can let some of these rocks tell us a story a story yeah because if you know how to listen a rock can tell you all about where it came from but how can a rock tell a story
15:40:well take this rock for example it's called nice yeah it is pretty nice yeah that too but the name nice is actually spelled differently from nice the word you might use to describe someone kind can you describe this bit of nice for me well it's got a bunch of wavy stripes in
15:58:it that kind of kind of reminds me of sedimentary rocks which can have different colored layers but I haven't seen any sedimentary rocks in my collection that have wavy layers that's a great observation Sam and these wavy lines might be telling us the story that
15:13:this nice used to be a sedimentary rock but over time it changed into a completely different kind of rock rocks can change from one kind to another yes they can we've already covered this a little bit when we talked about sedimentary ous rocks what do you remember about sedimentary rocks H
16:33:they're made of sediment which can be tiny pieces of rock that are broken down from bigger rocks they get compressed into a new rock exactly and what about ous rocks Ignus means fire so those rocks form when liquid rock cools down into a solid rock but where did that
16:52:liquid rock come from H well I guess it could have been hiding underground the whole time but if an old rock gets supered super hot maybe it would get so hot that it would melt into liquid you got it but we haven't learned about the third main kind of rock out there rocks
16:09:like this piece of nice we've got ous rocks which can be made by melting old rocks sedimentary rocks which can be made by breaking down old rocks into teeny tiny pieces and finally metamorphic rocks and how do metamorphic rocks form well just like the names Ignus and sedimentary the name
16:28:metamorphic gives us a bit of a Hint it sounds like Metamorphosis which I know is what happens when caterpillars turn into butterflies or moths so as a metamorphic rock just a rock that used to be another rock exactly it doesn't need to be melted or broken down it just
17:45:goes from being one type of rock to another and it turns out the same type of metamorphic rock might have different stories to tell for example some nice rocks start off as sedimentary rocks like Shale but others start off as an Ignus Rock like granite and then what
17:01:happened what makes them change well the rock would have been underground and for some reason the ground around it either got really hot but not hot enough to melt the rock or there was a bunch of extra pressure something started pushing on the Rock really really hard or maybe
17:19:it was a combination of both extra heat and extra pressure that sounds intense it is intense some metamorphic rocks are made when an old rock touches hot magma that's coming up through the Earth you know how heat can cook your food changing how it looks or feels well the
18:37:Magma's heat basically Cooks a rock into looking different too but that's not all some metamorphic rocks are made from the movement of the earth's tectonic plates plates like we have in the kitchen no not quite tectonic plates are kind of like giant puzzle pieces that make up
18:54:the Earth's crust but unlike a puzzle you can put together on a table tectonic plates are floating on layers of magma and water so they're constantly moving around and pushing up against one another wait I remember now when tectonic plates try to move past each other they can make earthquakes right
18:13:but all that pushing also means a lot of pressure so if you're looking for metamorphic rocks you might want to start with a map of the earth's tectonic plates and then go to places where two plates are touching so what exactly is changing inside a rock with all that
18:29:heat and pressure like how did this piece of nice get those funky Stripes well rocks are generally made up of smaller building blocks called minerals and if you apply enough heat and pressure you can rearrange those building blocks or even create different minerals Al together in either case
19:46:enough has changed that you've got yourself a completely different Rock you're a rock in my world Savannah sometimes a metamorphic rock can even show us how the heat and pressure twisted and folded those minerals because nice isn't the only metamorphic rock with foliation which is the word
19:04:that geologists use instead of stripes and foliation happens when pressure squeezes a rock's minerals so much they flatten out into layers whether the original Rock had layers or not check out this Granite which is an ous Rock the minerals have grown into fairly
19:20:large crystals but they aren't lined up very neatly but when Granite under goes a lot of heat and pressure like where two tectonic plates touch it turns into nice with a bunch of visible foliation that's neat but not all metamorphic rocks look like this for example the
20:38:sedimentary rock Limestone can turn into the metamorphic rock marble the heat and pressure is high enough to rearrange the limestone's minerals growing brand new crystals out of the same ingredients but it isn't high enough to squeeze the crystals into a bunch of different
20:52:layers when the marble is done forming I've heard of marble people use it to make statues yes they do I wonder if anyone has ever combined Limestone and marble to make a statue of a caterpillar turning into a butterfly that would be an extra great example of metamorphosis
20:08:so both ous and sedimentary rocks can turn into metamorphic rocks can metamorphic rocks turn into other metamorphic rocks they can for example with the right amount of heat and pressure the sedimentary rock Shale can become the metamorphic rock slate but if you take a piece of slate and expose it
20:27:to even more heat and pressure pressure you can turn it into a piece of shist and then that piece of shist can be melted down to make an ous rock or get broken down to make a sedimentary rock yep basically every kind of rock can turn into any other kind of rock geologists call it the rock cycle and
21:45:they show how it works using pictures like this let's see an ous Rock gets worn down and carried away a sediment that becomes sedimentary rock that sedimentary rock can go through metamorphosis to become metamorphic rock and when a metamorphic rock becomes so hot it melts into magma it'll eventually
21:04:become an ous rock all over again or maybe that metamorphic rock gets worn down to make a sedimentary rock which melts to form an ous rock that sounds exhausting it kind of does it's a good thing rocks can't get tired like we can tell that to my pet rock Gloria Dr Turtleman gave her to me she's my
21:24:favorite wow Gloria looks amazing but is she nice wait which nice are you talking about the rock nice or the kind nice how about both thanks for learning about rocks with Sam and me and Gloria it's been so fun visiting the fort do you have a favorite kind of rock does anyone
22:46:in your family or do any of your friends like rocks as much as Sam and I do why don't you ask them and we'll see you next time here at the Fort bye that's
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