1Hey, it's Danny.
2A few years ago, I went on a trip to the U.S. state of Alaska.
3While I was there, I got to visit these: glaciers.
4It was incredible to see so much ice and snow in one place.
5Someone named Emily has a question that has to do with ice.
6Let's call Emily now.
7Hi Danny.
8Hi Emily.
9I have a question for you.
10What was the Ice Age like?
11Oh, that's a great question!
12You might have heard of the Ice Age before.
13Maybe you've seen movies or books about the Ice Age that include animals we don't have today,
14like woolly mammoths and saber-tooth cats.
15Or maybe this is new to you.
16I'm curious, when you hear the words "Ice Age," what do you think of?
17I don't know how you answered,
18but I bet the image in your mind included, well, ice, lots of it.
19Maybe you pictured something like those glaciers in Alaska.
20Or animals surviving in the snowy, icy poles of the Earth.
21If you live somewhere that gets cold in the winter,
22maybe you pictured something you've seen closer to home,
23like icicles hanging off trees or piles of snow.
24And you're right!
25Simply put, an Ice Age is when Earth gets colder and icier.
26This has happened more than once
27over the billions of years that the Earth has existed.
28Scientists think there have been at least five major Ice Ages.
29The time people usually call "the Ice Age" is the most recent one.
30It began only 2.5 million years ago.
31During this Ice Age, the temperature of the Earth hasn't always been the same.
32It's gotten colder and less cold over years and years.
33But during the coldest period of the Ice Age,
34there was way more ice and snow than there is on Earth today.
35And that ice and snow lasted for thousands and thousands of years.
36Imagine what it would be like
37if, instead of having winter snow for a few months this year,
38it was cold and icy all year.
39And the next year.
40And the year after.
41And for the rest of your life.
42And on and on for thousands of years.
43You'd have to get pretty good at surviving in the cold, right?
44Well, turns out lots of living things did figure out how to survive through the Ice Age.
45All over the world, scientists have found remains of animals who lived through the Ice Age's coldest years.
46These ancient remains are fossils.
47Like, check this out!
48This is a fossil skeleton of a woolly mammoth.
49When it was alive, this huge animal looked similar to an elephant
50but with a big woolly coat of fur.
51This woolly mammoth skeleton was discovered in the U.S. state of Michigan.
52These days, much of Michigan usually gets cold and snowy in winter.
53But by summer, it heats up again and the snow melts.
54But back when this woolly mammoth was alive,
55Michigan was covered in ice and snow year-round.
56That thick fur coat helped this mammoth keep warm.
57But even at the Ice Age's coldest,
58not everywhere was snow and ice all the time.
59Actually, a lot of the Earth was not snowy during the coldest years of the Ice Age,
60including much of the United States.
61Still, even those not-snowy places didn't look like they do today.
62Because so much of the Earth's water was frozen in huge sheets of ice and snow,
63many areas not covered in ice had less water than they do today.
64Less water meant fewer thick forests and more places that looked like this:
65grasslands.
66Grasslands hosted some animals that couldn't survive in constant ice and snow.
67Like, check out this one!
68This is a sloth.
69These days, sloths tend to live high in the trees of tropical rainforests.
70But take a look at the bones of a sloth from the colder years of the Ice Age.
71Next to a human, the sloth looks huge!
72If that sloth tried to hang from a thin jungle branch, it would fall.
73This ancient animal is a giant ground sloth.
74These big creatures lived on the ground, feeding off grasses and other plants.
75Some animals that prowled grasslands back then were almost identical to the animals we have on Earth today.
76Like these guys: lions!
77Today, lions can only be found on the continents of Africa and Asia.
78But during the colder years of the Ice Age,
79they roamed across much of North America.
80And here's one Ice Age creature you might recognize: people!
81Humans survived through the coldest years of the Ice Age too.
82So in summary, an Ice Age is a period of millions of years when the whole Earth cools.
83But it's way more complicated than just ice all over the place.
84During the coldest years of the Ice Age,
85much of the Earth was covered in ice and snow year-round.
86But many places were not ice and snow in those years
87but instead, grasslands.
88From fossils, we've learned about many animals who lived during that time.
89Some we don't have on Earth anymore,
90like mammoths and giant sloths.
91And some we do, like lions and even humans!
92And there's more left to discover.
93Every year, we find more and more clues about these chilly years on our planet.
94Keep an eye out for discoveries near where you live!
95That's all for this week's question.
96Thanks for asking, Emily!