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Earth and Space Science
Dec 4, 2025
254
4 pages
Discover how scientists study Earth's interior through seismic waves and what they've learned about our planet's structure. Earth... Show more
When earthquakes happen, they produce different types of seismic waves that scientists use to "see" inside Earth. These waves act like X-rays for our planet, revealing what we can't directly observe.
Body waves travel through Earth's inner layers and come in two types. P-waves (primary waves) move faster and can travel through solids, liquids, and gases. They compress and expand material parallel to their direction of travel. S-waves (secondary waves) are slower and shake the ground perpendicular to their direction, like a rolling motion. Importantly, S-waves cannot travel through liquids.
Surface waves only travel along Earth's surface and cause the most damage during earthquakes. Love waves move the ground side-to-side horizontally, while Rayleigh waves roll along the ground like ocean waves, moving particles up and down or side-to-side.
💡 The fact that S-waves can't pass through the outer core provided scientists with a crucial clue that part of Earth's core must be liquid!
When an earthquake occurs, the focus is where it actually begins underground, while the epicenter is the point directly above it on the surface. By studying how these waves travel through Earth, scientists have discovered boundaries between layers. The Mohorovicic discontinuity ("Moho") marks where the crust meets the mantle, about 50 km deep. Scientists also found shadow zones where certain waves don't appear, helping them identify the core-mantle boundary called the Gutenberg discontinuity.
Earth is like a giant jawbreaker candy with different layers! The crust is the thinnest outermost layer, ranging from just 7-10 km thick under oceans (oceanic crust) to 35-40 km thick under continents (continental crust). Continental crust contains lighter rocks like granite with silicon, oxygen, and aluminum, while oceanic crust has denser basalt.
Beneath the crust lies the mantle, which extends about 2,900 km down and makes up a whopping 80% of Earth's volume. It's mainly composed of silicate rocks rich in silicon, oxygen, iron, and magnesium. The upper mantle and crust together form the rigid lithosphere , while the softer, partially molten layer below is the asthenosphere.
At Earth's center is the core, divided into two parts. The outer core is liquid iron and nickel that flows around the solid inner core, creating Earth's magnetic field. The inner core, despite intense heat, remains solid due to immense pressure—a phenomenon called pressure freezing.
🔍 How do we know the core is made of iron and nickel? Evidence comes from meteorites! Most meteorites contain iron and nickel, and likely formed from the same material as Earth. The density of these meteorites matches Earth's overall density when we account for the lighter crust and mantle.
Danish seismologist Inge Lehmann discovered in 1936 that Earth has a "core within a core" by studying seismic reflections, proving that while the outer core is liquid , the inner core must be solid.
Have you ever noticed how South America and Africa look like they could fit together? In 1912, scientist Alfred Wegener proposed the Continental Drift Theory, suggesting all continents were once a single landmass called Pangaea about 200 million years ago. This later split into Laurasia and Gondwanaland during the Jurassic period.
Evidence for this theory is compelling! The continental edges fit like puzzle pieces, and identical fossil remains of plants (Glossopteris) and freshwater reptiles (Mesosaurus and Lystrosaurus) appear on continents now separated by oceans. Mountain ranges align perfectly across continents, and coal deposits found in Antarctica suggest it once had a tropical climate near the equator.
Seafloor spreading, proposed by Robert Dietz and Harry Hess, expanded on Wegener's ideas. They discovered that new ocean floor forms at mid-ocean ridges while old seafloor gets destroyed at subduction zones. The East Pacific Rise is one of the most active seafloor spreading sites. Near these ridges, rocks are younger with thinner sediments, while rocks farther away are progressively older.
🧲 The discovery of magnetic reversal patterns in seafloor rocks provided the smoking gun for seafloor spreading! These magnetic "stripes" are mirror images on both sides of ocean ridges, proving new material is being added equally to both sides as the seafloor spreads.
Scientists found that the Earth's magnetic field occasionally flips—North Pole becomes South Pole and vice versa—due to changes in the outer core's flow. These reversals get recorded in rocks as they form at mid-ocean ridges, creating symmetrical magnetic patterns on both sides as the seafloor spreads apart.
The plate tectonic theory explains how Earth's crust is divided into moving plates that create earthquakes, volcanoes, mountains, and other geological features. This theory, developed by Robert Dietz and Harry Hess, revolutionized our understanding of Earth.
What drives these massive plates? Heat from Earth's core creates convection currents in the mantle. These work like a pot of boiling water—hot, less dense material rises while cooler, denser material sinks. As hot material reaches the upper mantle, it spreads out, pushing plates apart at divergent boundaries where new oceanic crust forms from cooling magma. When the material cools and sinks, it creates convergent boundaries where oceanic plates get pushed downward.
Two main forces drive plate movement. Ridge push occurs when older, denser oceanic crust sinks lower than newer crust at ridges, essentially creating a slide that pushes plates toward trenches. Slab pull happens when the weight of a subducting plate pulls the rest of the plate into the subduction zone—like a tablecloth sliding off a table when one end falls.
🌊 The oceans are constantly changing size due to these tectonic forces. The Pacific Ocean is actually shrinking as plates converge, while the Atlantic Ocean grows wider as seafloor spreading outpaces subduction!
When seafloor spreading happens faster than subduction, oceans grow wider (like the Atlantic). Conversely, when subduction outpaces spreading, oceans shrink (like the Pacific). This dynamic process continuously reshapes Earth's surface, moving continents to new positions over millions of years.
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.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
9
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
this lesson contains a summarized lesson regarding the origin and structures of the earthnas well as its 4 subsystems.
Earth and Space Sciencea study notes about magma and the process of magmatism
Earth and Space Sciencemarine science
Earth and Space ScienceThis talks about motion, work, energy and power and fluids motion.
Earth and Space ScienceThis talks about the bigbang theory, formation of solar system, plate tectonics , active and non-active volcanoes and earthquakes.
Earth and Space ScienceWhat are earthquakes and what causes them to happen?
Earth and Space ScienceApp Store
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
Discover how scientists study Earth's interior through seismic waves and what they've learned about our planet's structure. Earth may look solid from the surface, but beneath our feet lies a complex arrangement of layers with different compositions and properties that... Show more
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
When earthquakes happen, they produce different types of seismic waves that scientists use to "see" inside Earth. These waves act like X-rays for our planet, revealing what we can't directly observe.
Body waves travel through Earth's inner layers and come in two types. P-waves (primary waves) move faster and can travel through solids, liquids, and gases. They compress and expand material parallel to their direction of travel. S-waves (secondary waves) are slower and shake the ground perpendicular to their direction, like a rolling motion. Importantly, S-waves cannot travel through liquids.
Surface waves only travel along Earth's surface and cause the most damage during earthquakes. Love waves move the ground side-to-side horizontally, while Rayleigh waves roll along the ground like ocean waves, moving particles up and down or side-to-side.
💡 The fact that S-waves can't pass through the outer core provided scientists with a crucial clue that part of Earth's core must be liquid!
When an earthquake occurs, the focus is where it actually begins underground, while the epicenter is the point directly above it on the surface. By studying how these waves travel through Earth, scientists have discovered boundaries between layers. The Mohorovicic discontinuity ("Moho") marks where the crust meets the mantle, about 50 km deep. Scientists also found shadow zones where certain waves don't appear, helping them identify the core-mantle boundary called the Gutenberg discontinuity.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Earth is like a giant jawbreaker candy with different layers! The crust is the thinnest outermost layer, ranging from just 7-10 km thick under oceans (oceanic crust) to 35-40 km thick under continents (continental crust). Continental crust contains lighter rocks like granite with silicon, oxygen, and aluminum, while oceanic crust has denser basalt.
Beneath the crust lies the mantle, which extends about 2,900 km down and makes up a whopping 80% of Earth's volume. It's mainly composed of silicate rocks rich in silicon, oxygen, iron, and magnesium. The upper mantle and crust together form the rigid lithosphere , while the softer, partially molten layer below is the asthenosphere.
At Earth's center is the core, divided into two parts. The outer core is liquid iron and nickel that flows around the solid inner core, creating Earth's magnetic field. The inner core, despite intense heat, remains solid due to immense pressure—a phenomenon called pressure freezing.
🔍 How do we know the core is made of iron and nickel? Evidence comes from meteorites! Most meteorites contain iron and nickel, and likely formed from the same material as Earth. The density of these meteorites matches Earth's overall density when we account for the lighter crust and mantle.
Danish seismologist Inge Lehmann discovered in 1936 that Earth has a "core within a core" by studying seismic reflections, proving that while the outer core is liquid , the inner core must be solid.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Have you ever noticed how South America and Africa look like they could fit together? In 1912, scientist Alfred Wegener proposed the Continental Drift Theory, suggesting all continents were once a single landmass called Pangaea about 200 million years ago. This later split into Laurasia and Gondwanaland during the Jurassic period.
Evidence for this theory is compelling! The continental edges fit like puzzle pieces, and identical fossil remains of plants (Glossopteris) and freshwater reptiles (Mesosaurus and Lystrosaurus) appear on continents now separated by oceans. Mountain ranges align perfectly across continents, and coal deposits found in Antarctica suggest it once had a tropical climate near the equator.
Seafloor spreading, proposed by Robert Dietz and Harry Hess, expanded on Wegener's ideas. They discovered that new ocean floor forms at mid-ocean ridges while old seafloor gets destroyed at subduction zones. The East Pacific Rise is one of the most active seafloor spreading sites. Near these ridges, rocks are younger with thinner sediments, while rocks farther away are progressively older.
🧲 The discovery of magnetic reversal patterns in seafloor rocks provided the smoking gun for seafloor spreading! These magnetic "stripes" are mirror images on both sides of ocean ridges, proving new material is being added equally to both sides as the seafloor spreads.
Scientists found that the Earth's magnetic field occasionally flips—North Pole becomes South Pole and vice versa—due to changes in the outer core's flow. These reversals get recorded in rocks as they form at mid-ocean ridges, creating symmetrical magnetic patterns on both sides as the seafloor spreads apart.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The plate tectonic theory explains how Earth's crust is divided into moving plates that create earthquakes, volcanoes, mountains, and other geological features. This theory, developed by Robert Dietz and Harry Hess, revolutionized our understanding of Earth.
What drives these massive plates? Heat from Earth's core creates convection currents in the mantle. These work like a pot of boiling water—hot, less dense material rises while cooler, denser material sinks. As hot material reaches the upper mantle, it spreads out, pushing plates apart at divergent boundaries where new oceanic crust forms from cooling magma. When the material cools and sinks, it creates convergent boundaries where oceanic plates get pushed downward.
Two main forces drive plate movement. Ridge push occurs when older, denser oceanic crust sinks lower than newer crust at ridges, essentially creating a slide that pushes plates toward trenches. Slab pull happens when the weight of a subducting plate pulls the rest of the plate into the subduction zone—like a tablecloth sliding off a table when one end falls.
🌊 The oceans are constantly changing size due to these tectonic forces. The Pacific Ocean is actually shrinking as plates converge, while the Atlantic Ocean grows wider as seafloor spreading outpaces subduction!
When seafloor spreading happens faster than subduction, oceans grow wider (like the Atlantic). Conversely, when subduction outpaces spreading, oceans shrink (like the Pacific). This dynamic process continuously reshapes Earth's surface, moving continents to new positions over millions of years.
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.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
9
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
this lesson contains a summarized lesson regarding the origin and structures of the earthnas well as its 4 subsystems.
Earth and Space Sciencea study notes about magma and the process of magmatism
Earth and Space Sciencemarine science
Earth and Space ScienceThis talks about motion, work, energy and power and fluids motion.
Earth and Space ScienceThis talks about the bigbang theory, formation of solar system, plate tectonics , active and non-active volcanoes and earthquakes.
Earth and Space ScienceWhat are earthquakes and what causes them to happen?
Earth and Space ScienceApp Store
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
