Catastrophic Events

1. Catastrophic Events 8-2.3 Explain how Earth’s history has been influenced by catastrophes (including the impact of an asteroid or comet, climatic changes, and volcanic activity) that have affected the conditions on Earth and the diversity of its life-forms.

2. What is a catastrophic event? • changes in environmental conditions on Earth due to ... • impact of an asteroid or comet • climatic changes • volcanic activity

3. 1. Impact of an asteroid or comet

4. Most meteors burn up in the Earth’s atmosphere before striking the surface.

5. At the end of the Mesozoic Era… • many groups of animals disappeared suddenly.

6. Scientists hypothesize that a large asteroid or comet hit Earth • dust and smoke went into the atmosphere and cause climate changes, many forms of plant life died and the animals that depended on those plants for food • the major life forms that disappeared at this time were the dinosaurs

7. 2. Climatic changes

8. The Earth has many different climates • Climate is an ever-changing condition on Earth. • Early life forms were influenced by the climates produced by the forming atmosphere and oceans of Earth.

9. During the Paleozoic Era … • tropical climate on land and shallow warm seas • as different land environments formed and sea levels changed, new life forms developed. • other life forms that could not adapt or find suitable conditions, especially many marine species, disappeared.

10. During the Mesozoic era … • many climate changes occurred due to plate tectonics and the movement of landmasses • plants and animals that survived through this time had structures and systems that allowed for greater adaptations

11. During the Cenozoic era … • climate continue to change • major ice ages caused the climate to become much cooler as ice sheets and glaciers covered many areas of Earth • many mountain ranges formed causing climate differences due to elevation

12. 3. Volcanic activity

13. volcanic activity has always been part of our always changing planet Earth volcanoes are mainly found on plate boundaries

14. During Precambrian time… • volcanoes erupting were very common • but lava flows, ash clouds in the atmosphere, and heat made conditions for life forms extremely difficult • those simple life forms often did not survive

15. Volcanoes are created as landmasses collide (plate tectonics) • Volcanoes continued to be common in the Paleozoic and Mesozoic eras

16. Volcanoes can send ash and dust into the atmosphere • The Sun can be blocked for long periods of time. • Many of Earth’s processes can be disrupted and ultimately the life forms that depend on those processes can die.

17. The eras of Earth history can be studied due to the conditions on Earth, the effect of those conditions on life-forms, and the possibilities of rapid changes to both (environmental conditions and life forms) due to catastrophes.