8.E.6A.3 Construct explanations from evidence for how catastrophic events (including volcanic activities, earthquakes, climatic changes, and the impact of an asteroid/comet) may have affected the conditions on Earth and the diversity of its life forms.
Catastrophes have influenced Earth's History throughout Geologic TimeLearning Objectives:
Students will be able to 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. |
It is essential for you to know that along with the study of the geologic time scale, the changes in life forms, additions and extinctions, are often accompanied by changes in environmental conditions on Earth. These environmental changes have been influenced by the impact of an asteroid or comet, climatic changes, and volcanic activity.
The eras of Earth history can be studied in light of 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. |
Impact of an asteroid or comet
> Earth’s atmosphere protects the planet from many of the meteors that enter it, resulting in their burning up before striking the surface. > At the end of the Mesozoic Era, when reptiles, early birds and mammals thrived, many groups of animals disappeared suddenly. > Scientists hypothesize that possibly a large asteroid or comet impacted with Earth. This impact caused dust and smoke to rise into the atmosphere and cause climatic changes, as well as the dying of many forms of plant life and animals that depended on those plants for food. > A major life form that disappeared at this time was the dinosaur. Volcanic Activity
From the earliest days while Earth was forming to present day, volcanic activity has been part of the nature of this changing planet. > During the Precambrian time volcanic activity was one of the most natural events, 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 these conditions. > As continent collided and mountains built up due to plate tectonics, volcanoes also formed. Volcanic activity continued to be common in the Paleozoic era. During the rapid movement of plates in the Mesozoic era, collisions and subduction produced extensive volcanic activity around plate boundaries. > Plate boundaries are still the location of much of Earth’s volcanic activity. > Very explosive volcanic activity can send ash and dust high into the atmosphere where it is carried great distances around the Earth. The Sun can be blocked for long periods of time. This violent type of activity can disrupt many of Earth’s processes and ultimately the life forms that depend on those processes. |
Climatic Changes
> Earth’s environments have many different climates even today. Climate is an ever-changing condition on Earth. > Earliest life forms were influenced by the climates produced by the forming atmosphere and oceans of Earth. > Life on land developed and flourished in the tropical climates and warm shallow seas during the Paleozoic Era. Throughout this era 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. > 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, such as seed coverings for plant seeds and protective body coverings or constant internal temperature for animals. > During the present Cenozoic era, climate conditions 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 and due to location near those ranges. |
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