One of the most difficult topics in geology to internalize is \"Geologic Time\"
ID: 293981 • Letter: O
Question
One of the most difficult topics in geology to internalize is "Geologic Time" (i.e. the age of the earth)
When you hear stories about dinosaurs living 100 million years ago (mya) that sounds like a long time ago, but how long is it really? The Earth is 4.5 billion years old and our universe is 13.5 billion years old. That amount of time is extremely difficult to imagine. Hopefully, this discussion will help put the age of the earth in perspective.
For this discussion please watch the video below then create discussion post about whether your concept of geologic time has changed or what you found interesting about the video.
Earth's History Plays Out On A Football Field | NPR's SKUNK BEAR
Explanation / Answer
When you hear stories about dinosaurs living 100 million years ago (mya) that sounds like a long time ago, but how long is it really? The Earth is 4.5 billion years old and our universe is 13.5 billion years old. That amount of time is extremely difficult to imagine. How can you imagine 4.5 billion years old? and how does compare that amount of time humans have been around? Ageologist gave us the idea to use a football field as metaphorr.
At one endzone of football field we have got the present and the other end zone is the moment our planet formed(past 4.5 bya). Earth's entire history stretches the full 100 yards inbetween.Every inch is 1.3 million years. Let's start at the begining and take a walk through earth's entire history.For the first few hundred million years the earth was bombarded with rocks from outer space but now its starting to calm down (4.3 bya) and wayup here 3.8 billion years ago life begins. We are taking a simple life - single cells floating in a vast ocean. Now these cells figuring new ways to get energy - they are evolving to harness the power of the sun.Photosynthesis starts past the 20 yard line(3.6 bya). The air here is mostly carbondioxide and nitrogen but right around here little green (3.4bya). Cells starts making oxygen. And up here, about 2.8 billon years ago oxygen starts building up in the atomosphere (2.3bya). We are halfway down the field and we just got the kind of atmosphere that human can breathe (2.3bya).
For the next billion years and a half years it's paradise for single cells of every variety. As we move down the field cells start working together.And by the time we reach the 18 yard line there is lots of complex critters floating around. It's 800 million years before the present and things are about to get really interesting.Here at 13 yard line (0.6bya) , we have got an ozone layer. And here a sudden explosion of diversity Fungi(0.56bya),Sea Anemones(0.55bya), Molluscs(0.535 bya). 530 million years ago, animals take their first few steps on land. In the Ocean fish appear!, Land plants, Insects, Sharks , Amphibians. It's been 4 billion years since we started and here at the 5 yard line. We just starting to see the first mammals and dinosaurs.We see stegosaurus dinosaurs right here about 176 million years ago Stegosauria(0.176bya) but we don't see the T. rex untill about four and half feet from the end zone. About 68 million years ago Tyrrannosaurus(0.068bya) T-Rex is closer to us in the present than it is to the stegosaurus way back there and there is catastrophe at 1 yard line. 60 million years ago an asteroid, volcanoes? or climate change? are all three? killed 75% of all species(0.066bya mass exintinction). But life rallies this yard line is the yard of mammals.We have got armadillos(0.055bya) Gaint whales(0.04bya), Wolves(0.035bya). And here a foot away , the great apes our family(0.015bya). Hippos and Mammoths(0.005bya) , Lions (0.004bya), Lucky almost human(0.0032) but not quite. Sabertooth tigers (0.0025bya), Cattle (0.003bya) Then 200 thousand years ago , this is where we find humans (0.0002 bya) that look like us. That just just eight of a inch from end zone . Then all of human experiences, but evrything we call of civilization agriculture, cities, books, science etc.
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