When the cycle is broken

Discover Earth's mass extinction events: learn causes from volcanoes to asteroids!

Congratulations, you’re part of the 1 percent. That is, the 1 percent of species on Earth not yet extinct: For the last 3.5 billion or so years, about 99 percent of the estimated 4 billion species that ever evolved are no longer around. Almost since the beginning of life on earth (about 3.5 billion year ago) there have been great disruptions in the cycles that control earth's climate. We call them "mass extinctions". These events are defined as the loss of least 75 percent of total species on earth at one time in the geological blink of an eye — which can range from thousands to millions of years. Researchers have enough data from the fossil record going back just over half a billion years to identify five such mass extinction events, and many scientists believe we’re in the middle of a sixth mass extinction.Great die-offs result from a perfect storm of multiple calamities, such as ocean acidification coupled with an increase in land temperatures. While the catalysts of these events are sometimes unclear, large-scale volcanic activity, spread across an entire region, is a usual suspect. Theories that asteroid strikes initiate the massive die-offs remain largely speculative: Only one space rock has been conclusively linked to a mass extinction. The carbon cycle seems to be the main suspect in the extinction of 99% of all species that have ever lived on the earth since life began on earth. 1. Use the paragraph above to complete the section below. Almost since the beginning of life on earth (about 3.5 billion year ago) there have been great disruptions in the cycles that control earth's climate. We call them "mass extinctions". These events are defined as the loss of least 75 percent of total species on earth at one time in the geological blink of an eye — which can range from thousands to millions of years. Researchers have enough data from the fossil record going back just over half a billion years to identify five such mass extinction events, and many scientists believe we’re in the middle of a sixth mass extinction.Great die-offs result from a perfect storm of multiple calamities, such as ocean acidification coupled with an increase in land temperatures. While the catalysts of these events are sometimes unclear, large-scale volcanic activity, spread across an entire region, is a usual suspect. Theories that asteroid strikes initiate the massive die-offs remain largely speculative: Only one space rock has been conclusively linked to a mass extinction. The carbon cycle seems to be the main suspect in the extinction of 99% of all species that have ever lived on the earth since life began on earth. 2. Life began on earth about _ years ago. 350 million 350 billion 3.5 billion 30.5 billion 3. About what percent of species that have ever lived on earth are now extinct? 5% 25% 75% 99% 4. What is it called when a large number of species on earth becomes extinct? history mass extinction minor extinction big death 5. A mass extinction is when what percent of species dies off due to a common event? 75% 99% 25% 1% 6. In the paragraph above it says that an extinction can happen in "a geological blink of an eye". How long is that? tens to hundreds of years hundreds to thousands of years thousand to millions of years millions to billions of years 7. What is the most likely cause of MOST mass extinctions? meteor impact large scale volcanic activity many repeated asteroid impacts 8. We have learned that CO2is very effective at trapping heat energy in the atmosphere, and that this causes our climate to warm up. But all the previous mass extinctions happened long before there were humans around to burn fossil fuels and add carbon dioxide to the atmosphere. All fossil fuels - coal, oil and natural gas, for example - contain Carbon, and burning those fuels releases that carbon back into the atmosphere where it started. So, where did the added carbon come from that caused the climate to warm or the oceans to become more acidic and trigger mass extinctions BEFORE humans were around?9. One of the most abundant types of rock on earth is Limestone (CaC03) which is composed of Calcium, Carbon and Oxygen. Limestone stores a huge amount of calcium. It is a sedimentary rock made of seashells, and seashells are made of mostly carbon (as are most living things, including us. we are mostly Carbon, Hydrogen and Oxygen). Buried deep in the ocean floors all over the world, this layer of rock - many miles thick - is holding trillions of tons of CO2. Limestone is the main ingredient of cement. Smashing up limestone and adding other ingredients releases tremendous amounts of CO2 into the atmosphere. 10. When magma finds its way to the surface it also releases vast amounts of stored CO2. When scientists examine the rock record and search for clues to the causes of mass extinctions, a common factor is a large increase of CO2 in the atmosphere. One of the great extinctions in earth's history came after a period of extreme volcanic activity in what today is called Siberia in northern Russia.11. The last mass extinction, 65 million years ago, the one that saw the extinction of the dinosaurs and nearly all life on earth, was brought about by an asteroid impact. It is thought that the impact caused two events that worked together to end nearly all life: the ash, smoke and dust that was pushed high into the atmosphere covered the earth for several years before slowly filtering down to the surface. We find traces of these materials in layers of rock that are 65 million years old. This atmospheric debris blocked sunshine and caused the plant ecosystems to collapse. The atmospheric debris also trapped excessive amounts of heat, and caused the planet to warm by several degrees on average. Most animals on earth can adapt to small changes in their environment, but large changes that come about quickly are impossible for most organisms to adapt to. When the plant ecosystems collapsed, so did the ecosystems that depended on plants, and that was followed by ecosystems farther up the food chain. Very few species survived the last great extinction - a few species of birds and the early mammals were among those.12. In just the last 200 years humans have brought about the extinction of hundreds of species - some scientists say that number is likely in the thousands! Some of these species were hunted to extinction by humans, others could not adapt to the changes in the environment brought about by humans. Are we in the midst of a 6th mass extinction, is it being caused by humans? Time will tell, but today it appears we are! 13. Use the paragraphs above to sort the following items into either human caused, or nature caused. Choose a term below and decide if it is caused by humans, or if it is a natural event. Human-Caused burn fossil fuels cement species were hunted could not adapt to the changes in the environment brought about by humans Nature Caused magma finds its way to the surface extreme volcanic activity asteroid impact ash, smoke and dust that was pushed high into the atmosphere 14. Use the paragraphs above and your knowledge to match the words and terms on the left with those on the right. Building homes and highways use this cement oil, gas and coal are examples of fossil fuels burning fossil fuels adds CO2 to the atmosphere hunting human caused extinctions asteroid impact caused dinosaur extinction human caused changes to the environment animals can't adapt fast enough extreme volcanic activity when magma finds it way to the surface