Answer Key: Week One Homework
Review Questions
(a) oceanography; (b) geology; (c) meteorology or atmospheric science; (d) astronomy.
2) Our solar system formed from a rotating, cloud of gas, dust, and ice, referred to as a "nebula", approximately 4.6 billion years ago. A proto-Sun formed at the center of the nebula where the most mass existed. The rotating cloud of gas and dust flattened out an assumed a disk shape. Mass accumulated by "accretion" away from the center of the nebula -- to form protoplanets. The protoplanets grew in size, and became what is referred to as "planetesimals". As the proto-Sun grew in size it became hotter due to intense pressures, and eventually thermonuclear reactions within the sun occurred¾ a process referred to as fusion ¾ the conversion of hydrogen to helium, which releases tremendous amounts of energy.
3) The four spheres that constitute our environment are the hydrosphere, or water portion of the earth; the atmosphere, earth's gaseous envelope of air; the solid earth, consisting of the dense core, less dense mantle, and crust; and the biosphere, which includes all life on earth.
4) The three principle divisions of earth are the dense core; the less dense mantle; and the crust which is light and very thin outer skin of the earth.
- The oceans cover nearly 71% of earth's surface and contain about 97% of the planet's total water supply.
- In closed systems matter is self contained -- i.o.w., it stays within the system. In an open system both energy and matter flow into and out of the system. Most natural systems are open.
- Negative feedback mechanisms act to maintain the system as it is. Positive feedback mechanisms act to enhance or cause change in the system. Most earth systems contain a variety of negative and positive feedback mechanisms.
- The sun and heat from earth's interior provide energy for the earth system.
- Renewable resources are those that can be replenished over relatively short time spans. Examples include forest products, natural fibers, and wind energy. By contrast, nonrenewable resources form so slowly that significant deposits often take millions of years to accumulate. Practically speaking, therefore, earth contains fixed quantities of these substances. Examples include aluminum, copper, coal, natural gas, and petroleum.
- World population y reach 7 billion by the year 2010. Near the beginning of the 19th century, the world's population was about 1 billion people.
- Earthquakes, landslides, floods, and hurricanes are just four of many natural hazards.
- A scientific hypothesis is a tentative explanation that has not yet been tested. By contrast, a scientific theory is a well tested and widely accepted explanation for certain observed facts. As theories survive more testing they are regarded with higher levels of confidence.
Examing the Earth System
(1) a) mountain -- lithosphere; b) lake -- hydrosphere; c) tree -- biosphere; d) cloud -- hydrosphere (a cloud is comprised of liquid and solid water); ice and snow -- hydrosphere