earth science

Geological history of North America

Geological history of North America is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Geological history of North America rather than just read about it. In short: The geological history of North America comprises the history of geological occurrences and emergence of life in North America during the interval of time spanning from the formation of the Earth through to the emergence of humanity and the start of prehistory. At the start of the Paleozoic Era, what is now "North" America was actually in the Southern Hemisphere.

Key takeaways

Geological history of North America belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Geological history of North America to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Geological history of North America from memory before moving on to harder problems.

Reference excerpt

The geological history of North America comprises the history of geological occurrences and emergence of life in North America during the interval of time spanning from the formation of the Earth through to the emergence of humanity and the start of prehistory. At the start of the Paleozoic Era, what is now "North" America was actually in the Southern Hemisphere. Marine life flourished in the country's many seas, although terrestrial life had not yet evolved. During the latter part of the Paleozoic, seas were largely replaced by swamps home to amphibians and early reptiles. When the continents had assembled into Pangaea, drier conditions prevailed. The evolutionary precursors to mammals dominated the country until a mass extinction event ended their reign. The Triassic, the first period of the Mesozoic Era, followed. Dinosaurs evolved and began their rise to dominance, quickly spreading into the United States. Soon, Pangaea began to split up and North America began drifting north and westward. During the latter Jurassic, the floodplains of the western states were home to dinosaurs like Allosaurus, Apatosaurus, and Stegosaurus. During the Cretaceous, the Gulf of Mexico expanded until it split North America in half. Plesiosaurs and mosasaurs swam in its waters. Later into the period, it began to withdraw and the coastal plains of the western states were home to dinosaurs like Edmontosaurus, Triceratops, and Tyrannosaurus. Another mass extinction ended the reign of the dinosaurs. The Cenozoic Era began afterward. The inland sea of the Cretaceous gradually vanished and mammals were beginning to dominate the land. During the Eocene, the western states were home to small primitive camels and horses as well as the carnivorous creodonts. Soon, mammals had entered the oceans and the early whale Basilosaurus swam the coastal waters of the southeast. Rhinoceros-like titanotheres dominated Oligocene South Dakota. From this point on, the climate in the United States cooled until the Pleistocene, when glaciers spread. Saber-toothed cats, woolly mammoths, mastodons, and dire wolves roamed the land. Humans arrived across a land bridge between Siberia and Alaska and may have played a role in hunting these animals into extinction.

Precambrian

The oldest known eukaryotes lived around 1.4 billion years ago during the Precambrian near Beck Spring in California. These were photosynthetic organisms and produced oxygen as a byproduct of their physiology. The Beck Spring eukaryotes and other Precambrian photosynthesizers released the oxygen that now makes the planet's atmosphere breathable. Precambrian cyanobacteria remains from this age were preserved between Copper Harbor and Eagle Harbor on the shoreline of Lake Superior in the Upper Peninsula of Michigan. The appearance of the first eukaryotic cells in the fossil record were relatively followed by evidence of complex multicellular life. Rocks in Nevada dating back to a billion years ago preserve trace fossils left behind by worms as they burrowed below the sediment. Other complex Precambrian life forms were preserved in North Carolina and Arizona.

Paleozoic

The Phanerozoic eon began following the Precambrian. The first major unit of time it contained was the Cambrian period of the Paleozoic era. At the time, Earth's continents were in a very different arrangement and were generally smaller than they are today. The southeastern part of the US was connected to South America and Africa and located in the polar latitudes of the southern hemisphere. The western states were located near the equator. All known life during the Cambrian was aquatic so areas of the United States above sea level would have been sterile wastelands. Trilobites are the most common kind of animal in the Cambrian fossil record. Especially notable are the Elrathia of the Antelope Springs region of Utah. Sponge-like archaeocyathids were common in Nevada. Brachiopods, gastropods, and sponges were also important Cambrian animals. Sea levels around North America dropped at the end of the Cambrian. Ecosystems in shallow water probably devastated. The Cambrian ended with a mass extinction. Globally, brachiopods and gastropods lost much of their biodiversity, sponges lost about half of their families and almost three quarters of contemporary trilobite families vanished at the same time. Much of the continent would be submerged when the sea finally rose again. The most common animal in the Ordovician fossil record seems to have been brachiopods. Large numbers flourished and were preserved in great detail near Cincinnati during the Middle Ordovician. Members of this fauna were preserved in Indiana, Kentucky, and Ohio. Most known Ordovician trilobites are distinct from their Cambrian forebears as the few taxa surviving the mass extinction diversified once again. During the Middle Ordovician, early armored jawless fish called ostracoderms left behind fragmentary shards of bone in what is now the Rocky Mountains region. Late in the Ordovician sea levels dropped. Another mass extinction marked the end of the Ordovician. Globally, 25% of families disappeared. Major losses were experienced by brachiopods, fishes, echinoids, sponges and trilobites. This mass extinction was also most damaging to trilobites, which lost 50% of their families.

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Illustrations

Worked examples

Example 1 — a first encounter with Geological history of North America

Start with the simplest possible case. Write down what Geological history of North America claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Geological history of North America before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Geological history of North America ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Geological history of North America

In research: Geological history of North America appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Geological history of North America in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Geological history of North America is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geologic formations of North America, Natural history of Mexico, Paleontology in the United States, so understanding it makes those chapters shorter.
In everyday life: Look for Geological history of North America outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Geological history of North America in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Geological history of North America means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Geological history of North America out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Geological history of North America in simple terms?

Why does Geological history of North America matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Geological history of North America?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Geological history of North America.