on internal forcing factors: processes on Earth that influence climate. The major points

of the segment are number one, certain internal forcing factors, progeny, epeirogeny and volcanism

depends on tectonic movements of Earth's crust. Number two, albedo, the percentage of solar

energy reflected varies widely on different natural materials. Number three, Earth exchanges

energy with its surroundings in the form of electromagnetic radiation. Number four, electromagnetic

radiation can be characterized by its wavelength. Five, One-half of the electromagnetic radiation

from the Sun has wavelengths in the visible spectrum. Six, Greenhouse gases in the Earth's

atmosphere are transparent to visible light, but absorb in the infrared.

Internal forcing factors include orogeny, epeirogeny, volcanism, albedo and atmospheric

composition. Often these factors operate in conjunction with one another. For example,

volcanic activity may affect both Earth's albedo and atmospheric composition. The following

introduces each type of internal forcing factor and evaluates their current influence. Orogeny,

Greek for mountain building, is a process in which tectonic movements of Earth's crust

or volcanic activities from mountains. Mountains particularly with a north-south orientation,

for example, the Sierra Nevada, Rocky Mountains, Appalachian Mountains, Andes, and Euros disrupt

global atmospheric circulation patterns, that generally move east-west because of Earth's

rotation. Uplifting of mountains also moves and exposes rock that undergoes chemical weathering

and absorbs carbon dioxide. Moreover, higher elevations accumulate ice and snow that increases

Earth's albedo, the reflections of solar energy. For these reasons times of relatively rapid

mountain building, say 40 million years ago when the Himalayas and Sierra Nevadas first

arose are usually cooler periods.

Epeirogeny is the formation of continents and ocean basins through tectonic deprivations

of earth's crust. As discussed previously, global distributions of land masses determines

the amplitude of glacial/interglacial cycles, and at the extreme may foster a snowball earth.

In addition, mid ocean ridges where most of the new clay material is produced release

large amounts of energy and greenhouse gasses. Moreover, sea levels rise and fall as new

plate materials modify the shape of ocean basins. Orogeny and epeirogeny proceed slowly

over many millions of years. In contrast, volcanism can have an explosive effect on

climate. For example, when Mt. Pinatubo in the Philippines erupted in June of 1991 after

460 years of inactivity, it spewed vast amounts of sulfur dioxide and fine particles into

the upper atmosphere. These materials quickly spread over most of the world and formed a

haze of aerosols in the stratosphere that reflected enough sunlight to lower global

temperatures by as much as a half a degree Celsius for nearly two years. Volcanic eruptions

as large as Pinatubo, occur only every century or so. But the smaller, yet significant eruptions,

such as Mount Saint Helens and El Chichon occur every decade. All of these eruptions

release carbon dioxide a greenhouse gas that contributes to global warming, as well as

sulfur dioxide and fine particles that reflect some light and contribute to global cooling.

The amount of CO2 released from volcanoes however averages about 10,000 fold less than

from the burning of fossil fuels. Therefore on balance volcanic eruptions cool rather

than warm the planet.