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Dec 28, 2025
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Understanding Relative and Absolute Dating Techniques
Em
@mowers_mbbh
1 / 3
Earth's Historical Record
The rocks beneath our feet tell amazing stories about Earth's past! They record geological events and changing life forms like a history book, though many "pages" of this rocky record are missing.
Uniformitarianism is a fundamental principle that helps us understand Earth's past. Introduced by James Hutton, this idea tells us that the natural processes we see today (like erosion or volcanic eruptions) also operated in the past. This means "the present is the key to the past" - we can look at how rivers carve canyons today to understand how they formed millions of years ago.
Scientists use relative dating to figure out the order in which geological events happened. This method doesn't tell us exactly how many years ago something occurred, but rather which event came first, second, and so on. The Law of Superposition states that in undisturbed sedimentary rock layers, the oldest rocks are at the bottom and the youngest are at the top - just like a stack of pancakes!
Did you know? Scientists use the term "Deep Time" to describe Earth's incredibly long 4.5-billion-year history. That's so long that if Earth's history were compressed into a single day, humans would only appear in the last few seconds before midnight!
Several other principles help geologists read Earth's history. The Principle of Original Horizontality tells us that sediment is normally deposited in flat layers, so tilted or folded layers must have been disturbed after formation. The Principle of Cross-Cutting Relationships shows that anything cutting across rock layers (like a fault or volcanic intrusion) must be younger than those layers.
Dating Techniques
Have you ever tried to put together a timeline of events? Geologists do this all the time with rocks! They use clues in the rock layers to determine which came first, second, and so on.
When looking at rock formations, geologists apply principles like superposition and cross-cutting relationships. For example, if a fault cuts through sandstone but not the conglomerate above it, we know the fault happened after the sandstone formed but before the conglomerate was deposited. These principles help us arrange geological events in chronological order.
While relative dating tells us the sequence of events, absolute age dating gives us actual numbers - like saying something happened 65 million years ago instead of just "a long time ago." Radiometric dating is the most powerful absolute dating method, using the decay of radioactive elements as a natural clock.
Cool fact: Radioactive decay happens at a constant rate that doesn't change regardless of temperature, pressure, or other environmental conditions. This makes it an extremely reliable clock for measuring geological time!
Radioactivity occurs when an atom's nucleus is unstable. These unstable parent isotopes decay into stable daughter isotopes at a predictable rate. Scientists measure this rate using half-lives - the time it takes for half of the radioactive parent material to decay. After one half-life, half remains; after two half-lives, one-fourth remains, and so on. This predictable pattern helps scientists calculate ages of rocks that formed millions or even billions of years ago!
Measuring Deep Time
Imagine having a clock that can tell time not in hours but in millions of years! Radiometric dating works like this special clock, helping scientists determine the absolute age of rocks - the actual number of years since they formed.
The process works by measuring the ratio between radioactive parent isotopes and their daughter products in a rock. The older the rock, the more daughter product it contains because the parent isotope has had more time to decay. Since radioactive decay happens at a constant rate, scientists can calculate how long it took for the observed ratio to develop.
Using radiometric dating techniques, geologists have determined that the oldest rocks on Earth's surface are about 4.03 billion years old. But how did they determine Earth's age to be 4.5 billion years? They examined meteorites! Scientists believe these space rocks formed at the same time as our solar system, giving us the most accurate estimate of Earth's true age.
Mind-blowing fact: Carbon-14 dating can determine the age of organic materials like bones and wood, but it only works for materials up to about 75,000 years old. For older materials, scientists must use other radioactive isotopes with longer half-lives!
Different radioactive elements have different half-lives, making them useful for dating different time periods. Uranium-238 has a half-life of 4.5 billion years, perfect for dating very old rocks, while carbon-14 is better for dating relatively recent organic remains. By selecting the appropriate radioactive clock, scientists can determine ages throughout Earth's long history with remarkable precision.
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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
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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
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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
Understanding Relative and Absolute Dating Techniques
Em
@mowers_mbbh
Ever wondered how scientists figure out how old Earth and its rocks are? Discovering Earth's history is like reading a book where some pages are missing. Geologists use special methods to piece together the timeline of our planet and determine... Show more
Earth's Historical Record
The rocks beneath our feet tell amazing stories about Earth's past! They record geological events and changing life forms like a history book, though many "pages" of this rocky record are missing.
Uniformitarianism is a fundamental principle that helps us understand Earth's past. Introduced by James Hutton, this idea tells us that the natural processes we see today (like erosion or volcanic eruptions) also operated in the past. This means "the present is the key to the past" - we can look at how rivers carve canyons today to understand how they formed millions of years ago.
Scientists use relative dating to figure out the order in which geological events happened. This method doesn't tell us exactly how many years ago something occurred, but rather which event came first, second, and so on. The Law of Superposition states that in undisturbed sedimentary rock layers, the oldest rocks are at the bottom and the youngest are at the top - just like a stack of pancakes!
Did you know? Scientists use the term "Deep Time" to describe Earth's incredibly long 4.5-billion-year history. That's so long that if Earth's history were compressed into a single day, humans would only appear in the last few seconds before midnight!
Several other principles help geologists read Earth's history. The Principle of Original Horizontality tells us that sediment is normally deposited in flat layers, so tilted or folded layers must have been disturbed after formation. The Principle of Cross-Cutting Relationships shows that anything cutting across rock layers (like a fault or volcanic intrusion) must be younger than those layers.
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Dating Techniques
Have you ever tried to put together a timeline of events? Geologists do this all the time with rocks! They use clues in the rock layers to determine which came first, second, and so on.
When looking at rock formations, geologists apply principles like superposition and cross-cutting relationships. For example, if a fault cuts through sandstone but not the conglomerate above it, we know the fault happened after the sandstone formed but before the conglomerate was deposited. These principles help us arrange geological events in chronological order.
While relative dating tells us the sequence of events, absolute age dating gives us actual numbers - like saying something happened 65 million years ago instead of just "a long time ago." Radiometric dating is the most powerful absolute dating method, using the decay of radioactive elements as a natural clock.
Cool fact: Radioactive decay happens at a constant rate that doesn't change regardless of temperature, pressure, or other environmental conditions. This makes it an extremely reliable clock for measuring geological time!
Radioactivity occurs when an atom's nucleus is unstable. These unstable parent isotopes decay into stable daughter isotopes at a predictable rate. Scientists measure this rate using half-lives - the time it takes for half of the radioactive parent material to decay. After one half-life, half remains; after two half-lives, one-fourth remains, and so on. This predictable pattern helps scientists calculate ages of rocks that formed millions or even billions of years ago!
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
Measuring Deep Time
Imagine having a clock that can tell time not in hours but in millions of years! Radiometric dating works like this special clock, helping scientists determine the absolute age of rocks - the actual number of years since they formed.
The process works by measuring the ratio between radioactive parent isotopes and their daughter products in a rock. The older the rock, the more daughter product it contains because the parent isotope has had more time to decay. Since radioactive decay happens at a constant rate, scientists can calculate how long it took for the observed ratio to develop.
Using radiometric dating techniques, geologists have determined that the oldest rocks on Earth's surface are about 4.03 billion years old. But how did they determine Earth's age to be 4.5 billion years? They examined meteorites! Scientists believe these space rocks formed at the same time as our solar system, giving us the most accurate estimate of Earth's true age.
Mind-blowing fact: Carbon-14 dating can determine the age of organic materials like bones and wood, but it only works for materials up to about 75,000 years old. For older materials, scientists must use other radioactive isotopes with longer half-lives!
Different radioactive elements have different half-lives, making them useful for dating different time periods. Uranium-238 has a half-life of 4.5 billion years, perfect for dating very old rocks, while carbon-14 is better for dating relatively recent organic remains. By selecting the appropriate radioactive clock, scientists can determine ages throughout Earth's long history with remarkable precision.
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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Students love us — and so will you.
4.9/5
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4.8/5
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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