# What really killed the dinosaurs? (It wasn’t just the asteroid) - Sean P. S. Gulick

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Earth School

## Let’s Begin…

Sixty-six million years ago, near what’s now the Yucatán Peninsula, a juvenile sauropod feasted on horsetail plants on a riverbank. Earth was a tropical planet. Behemoth and tiny dinosaurs alike soared its skies and roamed its lands while reptiles and tentacled ammonites swept its seas. But, in an instant, everything would change. Sean P. S. Gulick details one of Earth's most devastating periods.

## Additional Resources for you to Explore

Let’s explore the effects of impacts on Earth by using some online tools. Astronomers track Near Earth Objects (NEOs) in order to calculate the sizes of the asteroids or comets, as well as the chances of an Earth-crossing orbit. A NASA-updated list of NEOs and their cumulative probability of striking Earth is available here, and it shows how most NEOs are quite small. However, there are some larger ones, such as the asteroid Bennu, that are certainly worth tracking. But how do we know the effects of differently sized asteroids if they were to strike Earth? It turns out it depends on a lot of factors, including the size, speed (velocity), density of the asteroid, and what part of Earth it hits (assuming it does not burst in the atmosphere), among many others.

To explore these possibilities, you can use the Earth Impacts Effects program, available here. You can enter the distance from which you are observing an impact (e.g., 100 km or 60 miles from the impact, the effects I would feel are…), the diameter and density of the asteroid, the velocity of the object, the angle at which it hits, and finally, what the target area of Earth is made of (e.g., ocean or lake of a specific depth, sedimentary rock like limestone or sandstone, or crystalline rock like granite or basalt).

As an exercise, try entering some of the asteroids from the SENTRY table into the Earth Impact Effects Program, including their density and velocity (find these by clicking on the name of the asteroid), and then have them hit different types of targets on Earth to explore the effects. Some questions that might come up are: How big does an asteroid have to be to actually hit the ground? Do the effects get worse if the density of the asteroid is greater? Does the angle at which the asteroid hits matter? What effects change if the asteroid hits water as opposed to land made of sedimentary or crystalline rock? What kinds of energies are released in your different impact scenarios (Hint: these can be very large numbers!)? Lastly, look at the probabilities in the SENTRY table to realize how incredibly small the chance of a major impact in the next couple centuries is—and to perhaps breathe a sigh of relief.

Have fun exploring and learning!

Images and references used in the creation of this animation:

Pixabay - Stock Images:
Sunflower - RayMark
Grass - Hundankbar
garbage - ds_30
Iceberg - Makabera
Polar bear - iribagrova8176

Paintings in the public domain:
Starry Night - Vincent Van Gogh
The Great Wave - Katsushika Hokusaï
Eiffel Tower - Georges Seurat
Black Mesa - Georgia O'Keeffe
Guernica - Pablo Picasso
Skrik & Solen - Edvard Munch
The Great Day of His Wrath - John Martin
The Slave Ship - William Turner

Sketchfab - All Sketchfab models are licensed under Creative Commons attribution (CC BY 4.0):
Triceratops - Zacxophone
Carnotaurus - Magorius
Tyrannosaurus Rex - Rigsters
Temple - Maks Sokolowski
Mouse - Just8
Saberwing - MooreLab
Frog - ffish.asia / floraZia.com
Rhododendron - ffish.asia / floraZia.com
Tsukushi Rose - ffish.asia / floraZia.com
Orchid - sarahGB
Wood stick - 3dhdscan
Wood louse - .hapto GmbH
Bush - Marbles
Lichen - Frank McMains
Aloa Vera - nedo
Lab - viklia
Lab gear - dercruz926
VHS - Terrible Hard
Old computers - sudreyskr
Lab machine - guillemvilah
Floppy disk - ocean
Machine - Klinepeter
Mission control console - TheoClarke
Old computer - Freepoly.org
Old nuclear computer - P3TroV
Osborne - Denis Afanasjev
vintage terminal - NoMoreFeelings

Watch the video and finish the Think section to complete the lesson.

We can save the world. Speed and Scale shows us how to unlock a cleaner, healthier and safer future by laying out a roadmap that will get us to net-zero carbon emissions by 2050. How’s it going to work? We need to electrify transportation, decarbonize the grid, fix food, protect nature, clean up industry and remove carbon. To learn how we’re going to do all that - and to learn how you can take action now - explore this page.

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• Lesson Plan created by TED Ed

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