How the Earth Works: A Quiz

Question: Which volcano erupted in 1883 with explosions that were heard 2,200 miles (3,500 km) away and an ash cloud that reached 50 miles (80 km) into the atmosphere?

Answer: An eruption of Krakatoa (Krakatau), a volcano on Rakata Island in the Sunda Strait between Java and Sumatra, Indonesia, was one of the most catastrophic in history. On May 20, 1883, one of its three cones became active. The climax was reached on August 27, with tremendous explosions that were heard 3,500 km (2,200 miles) away in Australia and propelled ash to a height of 80 km (50 miles).

Question: Which layer of Earth’s atmosphere consists of electrically charged particles that influence the propagation of radio waves?

Answer: The ionosphere is the region of Earth’s atmosphere in which the number of ions, or electrically charged particles, is large enough to affect the propagation of radio waves. The ionosphere begins about 50 km (30 miles) above the surface of Earth but is most distinct at altitudes above about 80 km (50 miles).

Question: What region of the atmosphere are most clouds and weather systems contained in?

Answer: Weather is a state of the atmosphere at a particular place during a short period of time. It occurs in the troposphere, the lowest region of the atmosphere, which extends from Earth’s surface to altitudes of 6-8 km (4-5 miles) at the poles and about 17 km (11 miles) at the Equator.

Question: What wetland ecosystem is characterized by wet, spongy, poorly drained peaty soil?

Answer: A bog is a type of wetland ecosystem characterized by wet, spongy, poorly drained, peaty soil. Bogs can be divided into three types: (1) typical bogs of cool regions, dominated by the growth of bog mosses, Sphagnum, and heaths, particularly Chamaedaphne, (2) fens, dominated by grasslike plants, grasses, sedges, and reeds, and (3) tropical tree bogs, in which the peat may be formed almost entirely from tree remains.

Question: Where are you likely to find P waves, S waves, Love waves, and Rayleigh waves?

Answer: Seismic waves—such as P waves, S waves, Love waves, and Rayleigh waves—are vibrations generated by an earthquake (as well as explosions and similar phenomenon) and propagated within Earth or along its surface.

Question: Which scientific discipline deals with the relative abundance, distribution, and migration of Earth’s chemical elements and their isotopes?

Answer: Geochemistry is a scientific discipline that deals with the relative abundance, distribution, and migration of Earth’s chemical elements and their isotopes. Until the early 1940s geochemistry was primarily concerned with defining elemental abundances in minerals and rocks.

Question: They move slowly and calve in the spring in cold polar waters. What are they?

Answer: Calving is the breaking away of chunks of ice from glaciers or ice sheets that become icebergs. Probably the first mention of icebergs was by St. Brendan, an Irish monk whose partly fictional writings suggest that he encountered a “floating crystal castle” on the high seas.

Question: Which device is used to measure atmospheric pressure?

Answer: A barometer is a device used to measure atmospheric pressure. Because atmospheric pressure changes with distance above or below sea level, a barometer can also be used to measure altitude.

Question: Which instrument records the ground oscillations caused by an earthquake, explosion, or other Earth-shaking phenomena?

Answer: A seismograph is an instrument that makes a record of the ground oscillations caused by an earthquake, explosion, or other Earth-shaking phenomenon. Although originally designed to record natural earthquakes, it has many other uses.

Question: Which scientific discipline is concerned with the description and classification of Earth’s topographic features?

Answer: Geomorphology is a scientific discipline concerned with the description and classification of Earth’s topographic features. Much geomorphologic research has been devoted to the origin of landforms.

Question: Which luminous phenomenon of the Earth’s upper atmosphere occurs primarily in high latitudes and takes many forms, including luminous curtains, arcs, bands, and patches?

Answer: An aurora is a luminous phenomenon of the Earth’s upper atmosphere that occurs primarily in high latitudes of both hemispheres; auroras in the Northern Hemisphere are called aurora borealis, or northern lights; in the Southern Hemisphere, aurora australis, or southern lights. Auroras are caused by the interaction of energetic particles (electrons and protons) from outside the atmosphere with atoms of the upper atmosphere. Auroras take many forms, including luminous curtains, arcs, bands, and patches.

Question: What is the most abundant metal in Earth’s crust?

Answer: Aluminum—a lightweight, silvery white metal of the boron group of the periodic table—is the most abundant metallic element in Earth’s crust and the most widely used nonferrous metal.

Question: Which scientist gave his name to zones of charged particles ranging from 3,000 to 20,000 km (1,800 to 12,000 miles) above Earth?

Answer: The Van Allen radiation belt consists of doughnut-shaped zones of highly energetic charged particles trapped at high altitudes in the magnetic field of the Earth. The zones were named for James A. Van Allen, the American physicist who discovered them in 1958. The inner region is centred approximately 3,000 km (1,800 miles) above the terrestrial surface. The outer region of maximum density is centred at an altitude of about 15,000 to 20,000 km (9,000 to 12,000 miles).

Question: What gas does the ocean absorb, thereby slowing the greenhouse effect?

Answer: The ocean absorbs large amounts of carbon dioxide and hence plays a major role in delaying its buildup in the atmosphere. Without the moderating effect of the ocean, the steadily increasing input of carbon dioxide into the atmosphere (due to the extensive burning of coal, oil, and natural gas) would result in the rapid onset of the greenhouse effect.

Question: What geologic theory holds that many of Earth’s surface features are caused by the rigid rocky crust sliding over a layer of partially molten rock?

Answer: The plate tectonics theory has a long and tortuous history, though the theory itself is elegantly simple. The surface layer of the Earth, 50 to 100 km (30 to 60 miles) thick, is assumed to be composed of a set of large and small plates, which together constitute the rigid lithosphere. The lithosphere rests on and slides over an underlying, weaker layer of partially molten rock known as the asthenosphere. The constituent lithospheric plates move across Earth’s surface and interact along their boundaries, diverging, converging, or slipping past each other.

Question: What is a term for the starting point of an earthquake?

Answer: The starting point of an earthquake, usually at some depth within the Earth, is called the focus, or hypocentre. The point immediately above the focus at the surface is known as the epicentre.

Question: What scientific discipline is concerned with the precise shape and dimensions of Earth?

Answer: Geodesy is the scientific discipline concerned with the precise shape and dimensions of Earth and their determination and significance.