15 Facts About Geologic Time That Made Our Brains Hurt

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Vote up the most surprising facts about geological time.

Have you ever wondered about the age of the planet? To grasp just how old the Earth is might take some major mind bending. It definitely requires familiarity with technical geologic terms. After all, geologic time is so broad that it's been divided into more than 20 categories and subcategories. There are eons, eras, periods, epochs, and ages - all of which form a complicated timeline of overlapping (and somewhat simplified) divisions of time. 

We've avoided as much technical jargon as possible here, but there's still a lot about geologic time that's just really difficult to wrap one's head around. Dinosaurs, volcanoes, and woolly mammoths... oh my! Take a look at some geologic timeline facts that might actually make steam come out of your ears! 


  • Woolly Mammoths Were Roaming The Earth When The Pyramids Were Built
    Photo: Membeth / Wikimedia Commons / Public domain
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    Woolly Mammoths Were Roaming The Earth When The Pyramids Were Built

    Species of woolly mammoths lived in North America, Europe, and Asia as far back as 300,000 years ago (if not before). By about 11,000 years ago, the number of mammoths on Earth had declined significantly, with only a few remaining in areas like Alaska, continental Siberia, and Wrangel Island in the Arctic.

    Most woolly mammoths died off about 10,000 years ago, but the Arctic group lived into the Egyptian Middle Kingdom, c. 2040-1786 BC. It was during the Old Kingdom, c. 2686-2181 BC, that the grandest of the pyramids were built. These include noteworthy structures like the Great Pyramid at Giza, constructed for Khufu (r. 2559-2566 BC).

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    Tyrannosaurus Rex And Stegosaurus Lived About 80 Million Years Apart

    The Tyrannosaurus rex, a carnivorous creature whose name means "king of the tyrant lizards," might be one of the best-known dinosaurs in the world. T. rex, for short, stood as high as 40 feet tall and could weigh as much as nine tons, according to archaeological evidence. T. rex dominated North America during the Cretaceous period, about 65 million years ago.

    Another commonly known dinosaur, the Stegosaurus, was an herbivore with a deadly, spiked tail that also lived in North America. Stegosaurus could be found during the late Jurassic period, about 150 million years ago. While it's common to see both T. rex and Stegosaurus together in popular culture representations of dinosaurs (like in movies from the Jurassic Park franchise), they actually existed as many as 80 million years removed from one another.

    This also means that T. rex lived closer to when humans were around than Stegosaurus.

  • Humans Have Existed For One-Thousandth As Long As The Dinosaurs Lived
    Photo: J.T. Csotonyi / Wikimedia Commons / CC BY 2.5
    1,107 VOTES

    Humans Have Existed For One-Thousandth As Long As The Dinosaurs Lived

    The first dinosaurs existed on Earth during the Triassic period, about 245 million years ago. As species evolved, the climate of the planet changed, and other factors influenced dinosaurs' survival; they lived through the Jurassic and Cretaceous periods and died off roughly 66 million years ago. This signaled the end of the Mesozoic Era and the start of the Cenozoic Era. 

    Geologic time classifications aside, dinosaurs were around for between 150 and 200 million years. In contrast, the first hominids appeared roughly 2 million years ago. Evidence indicates humans, or homo sapiens, first appeared 300,000 to 200,000 years ago. The time humans have been on Earth amounts to about one-thousandth of that boasted by the dinosaurs. 

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    During The Age Of The Dinosaurs, Volcanoes May Have Been Erupting On The Moon

    Scientists know the moon was volcanically active between 3.5 billion and 1 billion years ago, but images taken by the LRO spacecraft suggest volcanic activity continued long after that. In fact, three volcanic deposits are believed to be less than 100 million years old, and one might be less than 50 million years old. 

    The age of the dinosaurs, or Mesozoic Era, lasted between 245 million and 66 million years ago, which means volcanoes may have been erupting on the lunar surface during this time. As Space writes, "If only dinosaurs had invented telescopes, they might have seen lava occasionally oozing from the surface of the moon."