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Em
12/1/2025
Environmental Science
Fossils and Geologic Time Scale Notes
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Dec 1, 2025
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Fossils and Geologic Time Scale Explained
Em
@mowers_mbbh
1 / 3
Types of Fossils
Ever wondered why dinosaur bones feel so heavy? They've been petrified - literally turned to stone! When mineral-rich water soaks into bones and leaves minerals behind, it preserves the detailed internal structure of the original organism.
Fossils come in many fascinating forms. Molds and casts form when shells get buried and dissolved, leaving hollow spaces that sometimes fill with minerals. Compression fossils occur when pressure squeezes out liquids from buried organisms, leaving thin carbon films - perfect for preserving ancient plants and insects.
Impression fossils show fine details of an organism's external structure in mud or silt, while unaltered remains preserve organisms with little change in ice, tar pits, or amber. Don't forget trace fossils like footprints, burrows, and even fossilized poop (coprolites) that provide indirect evidence of prehistoric life!
Fun Fact: Amber fossils are actually hardened tree sap that trapped insects and small organisms millions of years ago, preserving them almost perfectly!
The Fossil Record
Not every creature that ever lived becomes a fossil. The fossil record represents just a fraction of Earth's past life forms, arranged by their relative ages. You're much more likely to become a fossil if you have two things: hard parts like shells, bones, or teeth, and you get buried rapidly before scavengers or bacteria can decompose you.
Scientists use fossils to match up rock layers from different locations through a process called correlation. They pay special attention to index fossils - species that existed for a short time but were geographically widespread. Finding the same index fossil in different places means those rock layers formed during the same time period!
Fossils tell us amazing stories about ancient environments. Finding coral fossils means that area was once a warm, shallow tropical sea. In Virginia, most fossils are marine organisms found in the Appalachian Plateau, Valley & Ridge, and Coastal Plain regions. Since brachiopod fossils (indicating shallow seas) are found in Virginia's mountains, we can conclude these mountains were once underwater!
Remember This: Fossils are most often preserved in sedimentary rock, not igneous or metamorphic rock. This is because sedimentary rock forms through the gentle processes of compaction and cementation that don't destroy delicate remains.
The Geologic Time Scale
The geologic time scale organizes Earth's history like chapters in an epic story. Scientists constantly update this timeline as they discover new evidence about our planet's past and the evolution of life.
The scale breaks time into increasingly smaller units: eons, eras, periods, and epochs. Surprisingly, about 88% of Earth's history belongs to the Precambrian time (made up of Hadean, Archean, and Proterozoic eons), when only single-celled life existed until the very end. The Phanerozoic Eon (meaning "visible life") is where fossils become abundant.
The three eras of the Phanerozoic Eon tell fascinating stories: the Paleozoic ("ancient life") saw the rise of insects, vertebrates, and non-flowering plants; the Mesozoic ("middle life") featured dinosaurs and the first flowering plants; and our current Cenozoic ("recent life") is characterized by mammals, birds, and abundant flowering plants.
Think About This: We currently live in the Holocene epoch of the Quaternary period of the Cenozoic era of the Phanerozoic eon - but some scientists propose we've entered a new epoch called the "Anthropocene," marking the significant impact humans have had on Earth's geology and ecosystems!
We thought you’d never ask...
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Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Fossils and Geologic Time Scale Explained
Em
@mowers_mbbh
Dive into Earth's ancient history as we explore fossils and the geologic time scale! These preserved remains and traces of ancient life help scientists understand what Earth was like millions of years ago and how life has changed over time.... Show more
Types of Fossils
Ever wondered why dinosaur bones feel so heavy? They've been petrified - literally turned to stone! When mineral-rich water soaks into bones and leaves minerals behind, it preserves the detailed internal structure of the original organism.
Fossils come in many fascinating forms. Molds and casts form when shells get buried and dissolved, leaving hollow spaces that sometimes fill with minerals. Compression fossils occur when pressure squeezes out liquids from buried organisms, leaving thin carbon films - perfect for preserving ancient plants and insects.
Impression fossils show fine details of an organism's external structure in mud or silt, while unaltered remains preserve organisms with little change in ice, tar pits, or amber. Don't forget trace fossils like footprints, burrows, and even fossilized poop (coprolites) that provide indirect evidence of prehistoric life!
Fun Fact: Amber fossils are actually hardened tree sap that trapped insects and small organisms millions of years ago, preserving them almost perfectly!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Fossil Record
Not every creature that ever lived becomes a fossil. The fossil record represents just a fraction of Earth's past life forms, arranged by their relative ages. You're much more likely to become a fossil if you have two things: hard parts like shells, bones, or teeth, and you get buried rapidly before scavengers or bacteria can decompose you.
Scientists use fossils to match up rock layers from different locations through a process called correlation. They pay special attention to index fossils - species that existed for a short time but were geographically widespread. Finding the same index fossil in different places means those rock layers formed during the same time period!
Fossils tell us amazing stories about ancient environments. Finding coral fossils means that area was once a warm, shallow tropical sea. In Virginia, most fossils are marine organisms found in the Appalachian Plateau, Valley & Ridge, and Coastal Plain regions. Since brachiopod fossils (indicating shallow seas) are found in Virginia's mountains, we can conclude these mountains were once underwater!
Remember This: Fossils are most often preserved in sedimentary rock, not igneous or metamorphic rock. This is because sedimentary rock forms through the gentle processes of compaction and cementation that don't destroy delicate remains.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Geologic Time Scale
The geologic time scale organizes Earth's history like chapters in an epic story. Scientists constantly update this timeline as they discover new evidence about our planet's past and the evolution of life.
The scale breaks time into increasingly smaller units: eons, eras, periods, and epochs. Surprisingly, about 88% of Earth's history belongs to the Precambrian time (made up of Hadean, Archean, and Proterozoic eons), when only single-celled life existed until the very end. The Phanerozoic Eon (meaning "visible life") is where fossils become abundant.
The three eras of the Phanerozoic Eon tell fascinating stories: the Paleozoic ("ancient life") saw the rise of insects, vertebrates, and non-flowering plants; the Mesozoic ("middle life") featured dinosaurs and the first flowering plants; and our current Cenozoic ("recent life") is characterized by mammals, birds, and abundant flowering plants.
Think About This: We currently live in the Holocene epoch of the Quaternary period of the Cenozoic era of the Phanerozoic eon - but some scientists propose we've entered a new epoch called the "Anthropocene," marking the significant impact humans have had on Earth's geology and ecosystems!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user