Questions at Vermilion Rim
1Over spring break, sixth grader Imani Castellanos and her uncle Desmond drove to three national parks in the Southwest. At Vermilion Rim, a made-up park based on real canyons in the region, the canyon walls show hundreds of meters of rock layers stacked like pages in a book. Imani kept a journal of questions during a ranger talk and at the visitor center.
2Ranger Farid Lindgren pointed out two layers. One is limestone full of fossil shells and corals, much like animals that live in warm, shallow seas today. Another is sandstone with long, slanting lines like the sides of desert sand dunes. These layers formed over many millions of years. The region's climate changed partly because the continent itself moved: plates drift only a few centimeters a year, but over 300 million years that adds up to thousands of kilometers. A thin layer of volcanic ash shows that a large eruption once dropped ash over the area.
3"Earth's climate has changed many times," the ranger said. "Scientists ask what is causing a change and how fast it is happening." Slow changes in Earth's orbit and in the tilt of its axis help start and end ice ages over tens of thousands of years. The Sun's energy output rises and falls a little in cycles of about 11 years. A very large volcanic eruption can put tiny particles high in the air that block some sunlight and cool Earth for a year or two.
4People also affect climate. Burning coal, oil and gas releases carbon dioxide (CO₂), and clearing forests adds more. CO₂ is a greenhouse gas: it traps heat near Earth's surface. Since 1958, scientists have measured CO₂ in air samples directly. For older times, they measure CO₂ in tiny bubbles of air trapped in ice sheets, some of it hundreds of thousands of years old. Thermometers have tracked Earth's temperature since the late 1800s, and satellites have measured the Sun's energy since the late 1970s.