1. (a) oceanography, (b) geology, (c) meteorology and
climatology, and (d) astronomy
2. Renewable resources are those that can be replenished
over relatively short time spans.
Examples include forest products, natural fibers, and wind energy. In
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, and natural gas.
3. World population may reach nearly 7 billion by the
year 2010. Near the beginning of the nineteenth century, the world's population
was about 1 billion people.
4. Earthquakes, landslides, floods, and hurricanes are
just four of many natural hazards.
5. A scientific hypothesis is a tentative explanation
that has not yet been tested. In contrast, a scientific theory is a well-tested
and widely accepted explanation for certain observed facts. As theories survive
additional repeated testing they are regarded with higher levels of confidence.
6. The theory for the origin of the solar system, called
the nebular hypothesis, states that approximately 5 billion years ago the
bodies of the solar system condensed from an enormous cloud. As the cloud
contracted and began to rotate, the proto-Sun began to form. The protoplanets
(planets in the making) formed from material that had condensed and accreted
inside the cloud. The inner planets (Mercury, Venus, Earth, and Mars) were
unable to retain appreciable amounts of the lighter components of the
primordial cloud, whereas the outer planets (Jupiter, Saturn, Uranus, and
Neptune) accumulated large amounts of hydrogen and other light materials
because of their much colder temperatures.
7. The four “spheres” that constitute our environment are
the hydrosphere, or water portion of 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.
8. 71 percent; 97 percent
9. The
crust, the thin rocky outer layer of Earth, is divided into oceanic and
continental crust. Oceanic crust is on average about 7 kilometers thick and is
composed of the igneous rocks basalt and gabbro. Continental crust averages
about 40 kilometers in thickness and consists primarily of granodiorite. Beneath the crust is the mantle, a solid
layer that extends down to a depth of about 2900 kilometers, and contains more
than 82 percent of Earth’s volume. The mantle is composed of a dense igneous
rock called peridotite. The innermost layer of Earth is the core, which is a molten sphere composed of an iron–nickel
alloy.
10. The asthenosphere, located between 70 and 700 kilometers below the surface of Earth, consists of approximately 10 percent melted rock. This zone lies wholly within the mantle. The lithosphere lies above the asthenosphere and includes the crust and part of the upper mantle (that part above the asthenosphere). The asthenosphere behaves plastically; the lithosphere is rigid.
11. Earth’s youngest mountains are located principally in two major
regions or zones. The circum-Pacific belt includes the mountains of the western
12. Shields are expansive, flat regions composed of deformed crystalline
rocks; they are located in the stable interiors of continents. Stable platforms
are also located in the stable interiors; they consist of a thin veneer of
sedimentary rocks that often cover the shields.
13. The three major regions of the ocean floor include continental
margins, deep-ocean basins, and oceanic (mid-ocean) ridges.
14. In an open system both energy and matter flow into and out of the
system. Closed systems are self-contained with regard to matter.
15. Positive feedback mechanisms
tend to enhance or drive changes in system. In contrast, negative feedback
mechanisms work to maintain a system as it exists (i.e., to maintain the status
quo).
16. The Earth system is driven by energy from two sources. The Sun
provides the energy that drives the external processes that occur in the
atmosphere and on Earth’s surface. Internal processes, such as plate tectonics
and volcanism, are driven by energy from the Earth’s interior. This internal
energy derives from leftover heat from
Earth’s origin and also from heat
produced by the decay of radioactive elements.