Earth Science Praxis

Which two ions are present at the highest concentration in seawater?

Na+ and Cl- The ions with the highest concentration in seawater are chloride (Cl-) and sodium ions (Na+).

Which of the following best describes how wood typically becomes petrified?

Water containing dissolved silica infiltrates the wood. In petrification, dissolved inorganic material replaces the original organic material.

Based on the diagram above, what is the average rate of movement of the plate on either side of the Mid‑Atlantic Ridge?

1.3cm/year

The new rock being formed at the crest of the Mid-Atlantic Ridge is composed mainly of which of the following types of rock?

45

If all the sediment grains in a sample are well‑rounded, material consisting of which of the following grain sizes would have the lowest porosity?

A mixture of all of the above A sediment sample composed of spheres of about the same size has about the same porosity no matter what the given size is, as long as the type of grain packing is the same. Porosity is decreased when smaller particles fill the spaces between larger particles.

Of the following groups of organisms, which appeared first in the fossil record?

Brachiopods

Which of the following pairs are clastic sedimentary rocks?

Conglomerate and shale Chemical sedimentary rocks are the result of processes such as evaporation or precipitation out of solution. Clastic sedimentary rocks are made of particles compressed or cemented together.

Japan, where frequent deep-focus earthquakes occur, is located at a

Convergent plate boundary The islands of Japan are parts of the volcanic island arcs. The Pacific Plate and the Phillippine Plate are being subducted beneath the Eurasian plate. A subduction zone is a convergent plate boundary where one plate moves beneath another and sinks into the mantle. Deep- focus earth quakes tend to occur at subduction zones.

Of the following, which is the best way for a scientist to date a lava flow that is now several meters below layers of sedimentary rocks?

Determining the relative amounts of certain isotopes in the basalt.

Which of the following minerals is a carbonate?

Dolomite Quartz and feldspar are both in the silicate class of minerals. Gypsum is a sulfate and dolmite is a carbonate.

If all glacial ice present on Earth today melted, which of the following areas would experience the largest amount of uplift due to postglacial rebound?

East Antarctica Antarctica is covered by a thick ice sheet. As ice sheets form, the crust is pushed down because of the added weight; when the ice melts, the crust rebounds.

Of the following, which is the largest source of the biogenic sediment on the ocean floor?

Hard parts of marine organisms When marine organisms (such as phytoplankton) die, their remains can sink to the ocean floor, and their hard parts can accumulate.

The maps above show the orientation of Earth's landmasses at four different times in geologic history. Which of the following gives the correct sequence, from first to last? I, II, III, IV

IV, II, I, III The present continents were derived from the supercontinent Pangaea through fragmentation and continental drift. The maps show several stages in this breakup.

Active volcanism has been observed on which of the following bodies in the solar system?

Io Io is a moon of Jupiter. Volcanic eruptions have been observed on Io.

Which of the following best helps explain why water is an agent in physical (mechanical) weathering?

It expands when it freezes. In mechanical weathering, rock is broken into fragments without involving chemical change. Water can go into tiny cracks in rocks. When the water freezes and expands, the force can enlarge the cracks and finally help split the rock.

Which of the following best helps explain why quartz is a common mineral in sedimentary rocks?

It is relatively stable in conditions found at Earth's surface. Quartz is a major component of some common igneous and metamorphic rocks, such as granite and quartzite. When these rocks weather, quartz grains are likely to survive because quartz is a relatively hard and insoluble mineral and therefore very resistant to physical and chemical weathering. Also, when the cement in a quartz sandstone dissolves, the resistant quartz grains may be transported and become part of another sedimentary rock.

Which of the following properties of water most directly helps account for its ability to dissolve many salts?

Its molecules are polar. Water is a good solvent for ionic compounds because water molecules are small and polar. There is a slight negative charge on the oxygen side of a water molecule and a slight positive charge on the side with the hydrogen atoms. The negative side of the water molecule is attracted to positive ions and helps pull them away from the crystal lattice, while the positive side is attracted to negative ions. In solution, the positive and negative ions are surrounded by water molecules (i.e., they are hydrated).

During which of the following months is Earth's orbital speed fastest?

January Earth is closest to the Sun in January and farthest away in July, so its orbital speed is fastest in January and slowest in July.

Which of the following types of fault is shown in the diagram? Arrows away from each other

Left-Lateral Strike Slip No vertical movement is indicated. The arrows show movement parallel to the strike of the fault. In a left-lateral strike-slip fault, the side opposite the observer appears to be displaced to the left.

Tightly formed anticlines and synclines are most likely to be associated with

Mountain belts An anticline is a fold in which each half dips away from the crest, and a syncline is a fold in which each half dips toward the trough. Large-scale folding of crust results in the formation of mountains.

Carbonate, sulfate, and halide minerals are found mostly in rocks in which part of Earth?

Near the surface Earth's crust contains many different types of minerals and rocks. For example, CaCO3CaCO3, CaSO4CaSO4, and NaClNaCl are some of the minerals that can form because of the evaporation of seawater. The mantle is composed mainly of iron- and magnesium-rich silicates. The core is composed mainly of iron and nickel.

The graph above shows the average water level of a river in North America over a period of one year (September-August). Of the following months, in which did the watershed of the river probably receive the least amount of precipitation?

October The water levels in streams general increase as a result of precipitation or snowmelt. From the trend in the graph, December through February is a time of relatively high precipitation, while September through November is a time of low precipitation.

Which TWO of the following are conditions that increase the chances that organisms will become fossilized?

Organisms have hard parts, such as shells or skeletons. Organisms are buried rapidly. Organisms are more likely to be fossilized when they have hard parts and when they are buried rapidly (so scavengers do not destroy them, so they do not decay, etc.).

In which of the following tectonic settings are the Hawaiian Islands located?

Over a hot spot The Hawaiian Islands are near the center of the Pacific Plate, not at a plate boundary. It is suggested that the Hawaiian Islands chain is the result of the Pacific Plate moving over a hot spot.

Which of the following is a result of thermohaline circulation in oceans?

Oxygenated water is brought to the deep ocean. Oxygen dissolves in surface water. Thermohaline circulation brings surface water deep into the ocean.

Astronomers use the Doppler effect to determine the

Recessional velocity of stars and galaxies The doppler effect is the apparent change in wave frequency when the source and observer are moving relative to each other.

Which of the following best describes cosmic background radiation?

Residual radiation from the big bang. At the time of the big bang, the universe was filled with intense radiation. Cooling has shifted this radiation to longer wavelengths (microwave). This radiation is known as cosmic background radiation and is beleived to exist in all of space.

Which of the following best accounts for the differences in the slopes formed by different rock layers in the walls of the Grand Canyon, as represented above?

Resistant rock layers form steep cliffs, while less-resistant rock layers form gentler slopes. The horizontal layers of sedimentary rock seen in the walls of the Grand Canyon are composed of alternating layers of sandstone, shale, limestone, and so on. The limestone layers in the Grand Canyon are quite resistant to weathering in the dry climate, while the shale layers tend to be less resistant. This leads to differential weathering and erosion, whereby the limestone layers yield steep slopes while the shale layers have gentler slopes.

Which THREE of the following are often associated with mid‑ocean ridges?

Rift Valley, A fracture Zone, A hydrothermal Vent Rift valleys form where tectonic plates diverge. Fracture zones and hydrothermal vents can also form at mid-ocean ridges. Deep-sea trenches are typically found at subduction zones.

Which of the following properties of surface seawater is plotted on the world map above?

Salinity In subtropical regions of the ocean, evaporation generally exceeds precipitation, thereby resulting in relatively high salinity of surface ocean waters. Abundant rainfall in equatorial areas results in lower salinity. The isolines summarize salinity, which is, on average, about 35 parts per thousand in surface ocean water.

The midpoint from the Sun to Uranus' orbit is closest to the orbit of which of the following planets?

Saturn The average distance between the orbits of the outer planets increases with the increasing distance of the planets from the sun. Uranus is about 2.9 x 10^9 km away from the sun, and saturn is about 1.4 x 10^9 km away from the sun.

Which of the following forces is responsible for the movement along a strike-slip fault such as the San Andreas Fault?

Shearing A strike-slip fault is a fault for which the movement is parallel to the fault's strike. Shear forces cause adjacent bodies to move past each other in opposite directions.

Which of the following processes most likely accounts for the features in the diagram above being out of alignment?

Soil Creep Soil Creep is the gradual downhill movement of soil and loose rock material on a slope. Material on the hillside shows evidence of moving downhill under the influence of gravity.

Which of the following statements about the Sun's influence on Earth is correct?

Solar energy powers the convection currents that can result in cloud formation and thunderstorms. The Sun heats ground unevenly, which causes relatively warm air to rise in certain areas and convection cells to form. As the air rises, water can condense and cumulus clouds can form. These clouds sometimes develop in cumulonimbus clouds.

Which of the following is the name of a large sea that formed as Pangaea broke apart?

Tethys The Tethys Sea formed when Pangaea broke apart into Gondwana and Laurasia.

A sample of radioactive material is monitored for one minute at hourly intervals by use of a Geiger counter, yielding the data in the table above. Which of the following statements is INCONSISTENT with these data?

The count rate will increase in the coming hours.

Which of the following best explains why the bands on an isochron map of the East Pacific Rise are wider than similar bands on an isochron map of the Mid-Atlantic Ridge?

The rate of spreading along the East Pacific Rise is greater than that along the Mid-Atlantic Ridge. Basalt is produced at mid-ocean ridges and moves away from the ridges as the plates diverge. The basalt can be dated. Isochrons that are farther apart indicate that the spreading rate is greater.

A student conducts an experiment on heat absorption using equal masses of soil and water in identical containers. The soil and water start out at the same temperature, which is lower than the air temperature. Which of the following will most likely be observed after the soil and water have been exposed to bright sunlight for 30 minutes?

The temperature of the soil will increase more than the temperature of the water. Water has a very high specific heat, so it takes more energy to increase the temperature of a given mass of water by one degree than to increase the temperature of the sam mass of soil by one degree. The temperature of the soil, therefore, will increase faster than the temperature of the water.

In which of the following ways is Earth unique with respect to the other planets in the solar system?

There is a significant amount of liquid water on earths surface. Earth has a significant amount of liquid water on its surface, and none of the planets do. Other planets have an atmosphere (Venus) , all the other planets orbit the Sun in the same direction, and Earth's orbit is close to circular.

Which of the following statements about dark absorption lines in the solar spectrum is correct?

They correspond to elements in the Sun's atmosphere. A hot, dense gas emits a continuous spectrum. The continuous spectrum of the Sun initially includes all wavelengths of visible light. When this radiation enters the relatively cool, less-dense gas cloud around the Sun, some of the radiation that matches energy-level differences in the atoms of the cooler gas is absorbed by the atoms. The resulting spectrum thus contains a series of dark absorption lines whose wavelengths are characteristic of elements in the relatively cool gas cloud.

When it is Tuesday in New York City, United States, and midnight at the international date line, what day is it in Tokyo, Japan?

Tuesday The international date line keeps calendars on the correct date for world travelers. The day is usually different on the two sides of the international date line. When it is midnight near the international date line, most or all of the world is on the same day.

The geographic area that is drained by a river and its tributaries is called

a drainage basin The surface water in a drainage basin converges and flows into a single stream or river, which flows into another body of water.

The phases of the Moon are caused by

changes in the relative positions of the Sun, Earth, and Moon The Moon does not emit its own light but reflects light received from the Sun. The half of the Moon facing the Sun is lit, and the phases of the Moon, as observed from Earth, depend on how much of the lit portion of the Moon is visible at the time of observation. The amount changes as the Moon revolves around Earth.

As water is pumped from a well within an unconfined aquifer, the resultant shape of the water table around the well is referred to as the

cone of depression When water is pumped out of an aquifer, the water table can dip down in that area.

The attractive force that most strongly influences the movement of astronomical bodies is the

gravitional Since the late 1600s, the motion of astronomical bodies has been modeled successfully using gravitational force. The other forces have little or no effect on the movement of astronomical bodies.