by Eric Braun
There have been several major ice ages throughout Earth’s history. The first was the Huronian Ice Age, which happened more than 2 billion years ago. Next was the Cryogenian Ice Age. It began about 850 million years ago. The Andean-Saharan Ice Age was about 450 million years ago, and the Karoo Ice Age about 360 million years ago.
Earth is actually in the middle of a fifth major ice age, which began about 2.5 million years ago. It is called the Quaternary Ice Age. It is known for having had several cooling periods during which glaciers expanded, and then warming periods, in which they retreated. These periods last for tens of thousands of years. The last glacial period began about 100,000 years ago and ended about 12,000 years ago. Currently, our planet is in the midst of an interglacial, or warm, period.
During the last glacial period, average temperatures plummeted by about 18 degrees Fahrenheit. With this extreme cooling, glaciers expanded to cover large areas of Antarctica, North and South America, Europe, and Asia.
But ice ages affect the planet in ways other than just covering areas in glaciers. As glaciers creep forward, their sheer size and weight reshapes the surface of the planet. They can carve out valleys and lakes and scrape hills from the landscape. Then when glaciers melt, they fill lakes with water, and the dirt and rock they bulldozed up gets left behind in hills.
Ice ages affect plants and animals too. The Andean-Saharan Ice Age caused Earth’s first mass extinction. As the planet cooled over millions of years, about 86 percent of all plant and animal life died out.
Another mass extinction happened during the Karoo Ice Age. Nearly 75 percent of plant and animal species died out.
During the last glacial period of the Quaternary Ice Age many large animals such as the woolly mammoth, cave bear, and saber-toothed cat died out. But smaller animals that could more easily adapt to the colder climate were able to survive. Birds migrated to warmer locations.
Humans also adapted to the changing climate. They relocated to escape the bitter cold. They built shelters and used fire to keep warm. Humans also made tools to help them hunt when food was scarce. Since the last glacial period, humans have become the most dominant species on the planet.
While Earth’s climate has gone through warm and cool periods, these changes are different than climate change. The planet’s natural cycles of cooling and warming occur slowly, over thousands to millions of years. But in just the last 100 years, the average global temperature has risen 1.33 degree Fahrenheit, largely due to human activity and pollution. This dramatic increase has affected Earth’s natural changes.
During the Quaternary Ice Age, scientists estimate that cycles of glacial and interglacial periods are occurring every 100,000 years. There is a cool period lasting about 90,000 years followed by a warm period of about 10,000 years. Under natural circumstances, temperatures should be getting cooler right now, leading to a new glacial period. But that’s not what is happening.
Human activity is leading to a change in our naturally occurring climate. It could push the next glacial period off for another 100,000 years. This huge change could threaten the world as we know it. Scientists continue to study the affects of climate change and how we might be able to slow or stop it.
TIMELINE OF EARTH’S ICE AGES
Precambrian Era: Life on Earth Begins (4.6 billion years ago-542 million years ago) 2.4-2.1 Billion years ago: During the Huronian Ice Age; only single-celled organisms exist.
850-630 million years ago: The Cryogenian Ice Age occurs; likely due to new, multi-celled life forms using up much of the carbon dioxide in Earth’s atmosphere.
Paleozoic Era: Plants, Fish, Amphibians, and Reptiles Begin to Populate Earth. (542-251 million years ago) 450-420 million years ago: The Andean-Saharan Ice Age leads to a major extinction of plants and animals. More than half of life on Earth dies out.
360-260 million years ago: The Karoo Ice Age leads to another mass extinction that seems to affect only sea creatures.
Mesozoic Era: Dinosaurs Dominate Earth. (251-65 million years ago) 251-65 million years ago: Dinosaurs dominate during this time, but it is also the age when mammals, birds, and flowering plants develop.
Cenezoic Era: Mammals Become the Dominant Animal Life on Earth. (65 million years ago-Present) 2.5 million Years ago to present: The Pleistocene Epoch marks the beginning of the most recent ice age. During this time there are several glacial and interglacial periods.
12,000 years ago to present: The Holocene Epoch takes place. Humans become the dominant species on Earth.
OTHER PATHS TO EXPLORE
The characters in this book accidentally travel back in time. But what if you traveled back to prehistoric times on purpose? What tools would you bring? What would your goal be?
What if prehistoric beasts could time travel to the present day? What kinds of trouble might they cause for humans? How do you think people could best handle the situation?
If you could go back in time and live during prehistoric times, what era would you choose? Would you choose to roam the land with dinosaurs or come face-to-face with Ice Age megafauna? What type of environment would you want to live in? How would you survive?
READ MORE
Alonso, Juan Carlos & Gregory S. Paul. The Early Cretaceous. Lake Forest, CA: Walter Foster Jr., an imprint of Quarto Publishing Group USA Inc., 2017.
Mason, Paul. Dinosaur Hunters in the Forest. Minneapolis: Hungry Tomato, 2018.
Allman, Barbara. Glaciers. New York: Enslow Publishing, 2020.
INTERNET SITES
History.com: Ice Age
history.com/topics/pre-history/ice-age
Jurassic Landscape
nationalgeographic.com/science/prehistoric-world/jurassic/
National Geographic: Cretaceous Period
nationalgeographic.com/science/prehistoric-world/cretaceous/
GLOSSARY
canopy (KA-nuh-pee) —
the middle layer of the rain forest with thick greenery and little sunlight
carnivore (KAHR-nuh-vohr) —
an animal that eats meat
climate (KLY-muht) —
the usual weather in a place
diorama (dy-uh-RA-muh) —
a three-dimensional replication of a scene, often a miniature version
evolve (i-VAHLV) —
to change gradually, especially concerning animals or plants
extinct (ik-STINGKT) —
an animal that has died out, with no more of its kind
forage (FOR-ij) —
searching, especially for food
fossil (FAH-suhl) —
the remains of an ancient plant or animal that have hardened into rock; also the preserved tracks or outline of an ancient organism
glacial (GLAY-shul) —
describes a period during which glaciers expand due to cooling temperatures
gore (GORE) —
to pierce with horns
herbivore (HUR-buh-vor) —
an animal that eats plants
hypothermia (hi-puh-THUR-mee-uh) —
a life-threatening condition that occurs when a person’s body temperature falls several degrees below normal
lagoon (luh-GOON)—
a shallow area of water between the coast and a coral reef that’s offshore
megafauna (MEG-uh-fawn-uh) —
large animals that lived around the time of the Ice Age
omnivore (OM-nuh-vor) —
an animal that eats both plants and other animals
Pangaea (pan-JEE-uh) —
a landmass believed to have once connected all Earth’s continents together
predator (PRED-uh-tur) —
an animal that hunts other animals for food
prehistoric (pree-hi-STOR-ik) —
from a time before
history was recorded
prey (PRAY) —
an animal hunted by another animal
ray (RAY) —
a type of fish with a flat body, winglike fins, and a whiplike tail
sauropod (SORE-oh-pod) —
one of a group of dinosaurs with long necks, thick bodies, and long tails
terrarium (tuh-RER-ee-uhm) —
a clear container used to raise land animals or as a display case
tundra (TUHN-druh) —
a cold area where the soil under the ground is permanently frozen
SELECT BIBLIOGRAPHY
“Cretaceous Period.” National Geographic.com. www.nationalgeographic.com/science/prehistoric-world/cretaceous/>, Accessed March 20, 2019.
“Early Cretaceous Period,” HowStuffWorks.com. animals.howstuffworks.com/dinosaurs/early-cretaceous-period.htm, Accessed March 19, 2019.
“Late Cretaceous Period,” HowStuffWorks.com. animals.howstuffworks.com/dinosaurs/late-cretaceous-period.htm, Accessed March 19, 2019.
“The Big Five Mass Extinctions,” COSMOS: The Science of Everything, cosmosmagazine.com/palaeontology/big-five-extinctions, Accessed June 24, 2019.
“When Have Ice Ages Occurred?” Illinois State Museum, iceage.museum.state.il.us/content/when-have-ice-ages-occurred, Accessed June 24, 2019.
Britannica: Jurassic Period. www.britannica.com/science/Jurassic-Period, Accessed June 24, 2019.
Carr, Ada, “We’re Due For Another Ice Age But Climate Change May Push It Back Another 100,000 Years, Researchers Say,” The Weather Channel, weather.com/news/climate/news/ice-age-climate-change-earth-glacial-interglacial-period, Accessed June 24, 2019.
Dinosaur Timeline Gallery, www.prehistory.com/timeline/jurassic.htm, Accessed June 24, 2019.
Dixon, Dougal. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Leicester, UK: Southwater, 2014.
Everhart, Mike. Sea Monsters: Prehistoric Creatures of the Deep. Washington, D.C.: National Geographic Society, 2007.
Jurassic Period Facts, www.livescience.com/28739-jurassic-period.html,Accessed June 24, 2019.
Paul, Gregory S. The Princeton Field Guide to Dinosaurs: Second Edition. Princeton, NJ: Princeton University Press, 2016.
Poinar, George, Jr. and Roberta Poinar. What Bugged the Dinosaurs? Insects, Disease, and Death in the Cretaceous. Princeton, NJ: Princeton University Press, 2008.
Salleh, Anna, “Ice Age Australians Sheltered in Caves,” News in Science, September 24, 2007, www.abc.net.au/science/news/stories/2007/2039661.htm, Accessed June 24, 2019.
The Jurassic Period, www.nationalgeographic.com/science/prehistoric-world/jurassic/, Accessed June 24, 2019.
University of St. Andrews, “The Last Ice Age,” July 3, 2014, phys.org/news/2014-07-ice-age.html, Accessed June 24, 2019.
INDEX
Acrocanthosaurus, 31, 33
Alamosaurus, 81, 83, 88, 90
Allosaurus, 144, 165, 174, 180, 182, 189-190, 204, 211
Ankylosaurus, 92-93, 94
Archaeopteryx, 158, 159, 161
Brachiosaurus, 124, 140, 150, 174
cave bears, 222, 266-267, 273, 274, 276, 280
cave paintings, 259-260, 269-270, 277, 280, 281
Ceratosaurus, 130, 133, 134, 135, 141, 143, 174, 200, 204
Chicxulub asteroid, 100, 102, 106-107
Clovis people, 228, 251
Compsognathus, 171-172
Cro-Magnons, 223, 259, 262-263, 264, 266, 276-277, 278-279
Deinonychus, 37-38, 40, 41
Diplodocus, 193, 195, 200, 202, 211
Diprotodon, 284, 297, 299, 306, 307
Genyornis, 292, 294, 300, 304-305
Hypsilophodon, 30-31, 33, 34-35
Lambeosaur, 44, 46, 48, 51, 54, 62
multituberculates, 15, 20– 21, 30, 35, 60, 106
Neanderthals, 223, 251, 259
Pachycephalosaur, 61
Pangaea, 212
Procoptodon, 284, 287, 289-290, 297
pteranodons, 11, 81
saber-toothed cats, 222, 228, 233, 235, 241, 243, 245, 254
Spinosaurus, 24, 26, 106
Stegosaurus, 115, 116, 144, 157, 161, 163, 166, 167, 169, 174, 176, 178, 179, 211
Triceratops, 11, 38, 45, 64, 96-97, 106
Troodon, 78, 80, 84, 86
Tyrannosaurus rex, 51, 54-56, 62, 66, 68, 71, 96, 106, 115, 200
woolly mammoths, 228, 230, 232, 236, 237-238, 254, 264, 268-270, 272
You Choose Books are published by Capstone Press, an imprint of Capstone.
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Library of Congress Cataloging-in-Publication Data
ISBN: 978-1-4966-9725-7 (paperback)
ISBN: 978-1-9771-5937-3 (eBook PDF)
ISBN: 978-1-9771-5729-4 (eBook)
Summary: Leads readers through prehistoric adventures in which they can choose what to do and where to go next.
Cover Art
Alessandro Valdrighi (middle and bottom), Juan Calle (top)
Design Elements
Capstone and Shutterstock: Art studio G, DianaFinch, Miceking, Studio Photo MH, tinkivinki
Editorial Credits
Editor: Mandy Robbins; Designer: Bobbie Nuytten; Media Researcher: Jo Miller; Production Specialist: Tori Abraham
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