exposure to acids. Rainwater absorbs carbondioxide from the atmosphere and organic acidsfrom soil to become slightly acidic. Atmosphericpollutants, such as the oxides of sulfur and nitro­gen, can make rainwater unnaturally acidic.When limestone is exposed to these acids, theacids react with the calcite in the limestone. The

product of the reaction is soluble in water and iscarried away by water.

QUESTIONS _

PorfA -

1. Chemical weathering is most active is a cli­mate that is (1) warm and dry (2) warmand moist (3) cold and dry (4) cold andmoist

2. If you leave a bottle of water outside on acold winter night, the water may freeze,causing the bottle to break. This is an exam­ple of (1) physical weathering (2) chemi­cal weathering (3) water erosion (4) iceerOSIOn

3. The rock below was exposed at Earth's sur­face for a long time. What caused layers Aand B to be different from layers X and Y?

(1) Layers A and B were more exposed tothe elements than layers X and Y (2) Lay­ers A and B are composed of minerals withlower numbers on Mohs scale. (3) LayersA and B have less mineral cement than and

are softer than layers X and Y." (4) LayersA and B contain minerals more resistant to

weathering than layers X and Y.

4. Which property probably has the least effecton the rate at which a rock weathers?

(1) how long it is exposed to the atmosphere(2) the average density of its minerals(3) the hardness of the minerals (4) howmuch surface is exposed

5. What is the most common form of weather­

ing at high-latitude and high-altitude loca­tions? (1) frost action (2) chemicalweathering (3) mineral changes (4) solu­tion in water

6. An iron nail will rust when it is left outside.

What type of weathering is this? (1) frostwedging (2) rock abrasion (3) physicalweathering (4) chemical weathering

7. What natural process is best represented bythe diagram below?

~+~60 ...•~+ .-'ftJI U b )-:~;~:f~.;"' -~---

Feldspar Water Salts of calcium, Clay mineralspotassium, and (less than 0.0004 cm)

sodium dissolvedin water

(1) frost wedging (2) rock abrasion(3) physical weathering (4) chemicalweathering

8. A student broke the piece of rock shownbelow from a much larger rock. The arrowpoints from what was the outer surface ofthe large rock toward the former inside. Thechange in color by the arrow shows a formof weathering similar to

(1) water expanding when it freezes tobreak a metal pipe (2) a rock being rolledalong the bottom of a fast-moving stream(3) the body of a car decomposing due to ex­posure to salt and water (4) very small par-

earl~B~,.~_~-~=~--,=.:

10. The diagram below represents a cross-sec­tional profile of a particular location.

Rome Trieste Rome Milansandstone shale sandstone limestone

11. Which best explains why the mass of eachrock sample remaining after 30 minutes ofshaking was different? (1) Each rock wasin a different container. (2) Some rockshad more initial mass than others.

(3) Some rocks were shaken longer thanothers (4) Each rock had a different com­position.

U. How did the amount of shale changethrough time? (1) The mass increased, butit increased most quickly at the beginning.(2) The mass increased, but it increasedmost quickly at the end. (3) The mass de­creased, but it decreased most quickly at thebeginning. (4) The mass decreased, but itdecreased most quickly at the end.

13. Which rock type was most easily weatheredby abrasion? (1) shale (2) marble (3) rocksalt (4) limestone

14. What percent of shale remained after 30minutes? (1) 10% (2) 25% (3) 50%(4) 100%

Triesteshale

Florencebasalt

ticles of sediment blown around due to

strong winds

9. In moist climates where temperatures alter­nate between warm days well above O°Cand cold nights well below O°C, why dorocks break apart? (1) Cooling causesrocks to expand. (2) Frost forms when icemelts. (3) water expands when it freezes(4) water boils and contracts at 100° C

Which rock type appears to best resistweathering and erosion? (1) Rome sand­stone (2) Florence basalt (3) Milan lime­stone (4) Trieste shale

Base your answers to questions 11 through 16on thefollowing data table. The data are the re­sults of an experiment in which a student shook,one type at a time, 200 grams of four types ofdifferent rocks mixed with water.The rocks wereshaken with equal energyfor a total of 30 min­utes.

15. This experiment was an investigation ofrock (1) weathering (2) transportation(3) erosion (4) foliation

16. Compared to the original samples, howwould the appearance of rock particles havechanged? The rock particles remainingwould be (1) more angular (2) larger(3) more rounded (4) softer

17. In which month is physical weathering likelyto be especially active and chemical weath­ering relatively inactive in New York State?(1) January (2) April (3) July (4) October

Mass of Rock Sample Remaining (g)

Rock-Shaking~---~,.~'-'-~-~

Rock HOW DO SOilS FORM?Time (min)

ShaleMarbleSaltLimestone

0

200200200200Soil is the mixture of weathered rock, microor-

ganisms, and organic remains that usually covers5

160200120200 bedrock. The texture of a soil depends on the

10

12520060195size of the particles it contains. Clay-rich soils

tend to feel smooth. Soils rich in sand are more15

10019020170 likely to feel gritty. The composition of a soil de-

20

751800150pends on the rocks from which it weathered and

the local climate. Under natural conditions, bio-25

551750135 logical,physical,andchemicalweathering

30

501750125processes are usually involved in the develop-

ment of soils.

£0.Q)o'0(fJ

Time-

(1) A (2)B (3)C (4)D

20. The composition of a soil that formed inplace is primarily a function of (1) the ele­vation above sea level (2) the average an­nual temperature (3) the minerals in thebedrock (4) the age of the bedrock

21. Most plants grow best in a soil that is com­posed of (1) solid bedrock (2) only organicmaterial (3) broken up fragments ofbedrock (4) weathered rock and organicmaterial

22. Which of the following changes would mostlikely cause the soils in New York State tobecome thicker? (1) frequent floods(2) dryer conditions (3) increased biologi­cal activity (4) longer winters with littlesnowfall

Base your answers to questions 23 and 24 onthe photo below, which shows a soil profile ex­posed by beach erosion along a rocky shoreline.Unlike layers A, B, and C, layer D is solidbedrock.

QUESTIONS _

Figure 4-6. In some New York State locations, glaciers

have scraped away the soil and there has not been

enough weathering and time for new soil to form.

Protecting the SoilSoil is a resource that must be protected. It maytake' hundreds of years for just 1, centimeter oftopsoil to form. Human technology has con­tributed to the loss of soil. For example, con­struction and mining projects have moved greatamounts of rock and soil from their original 10­cations. Destruction of plant cover and poorfarming and forestry practices have left soil ex­posed and unprotected. Running water andwind quickly carry away the exposed soil.

Salt used to remove ice from roads in winteris washed into the soil at the side of the road. Ifthe concentration of salt in the soil is highenough, plants will not grow there. Withoutplants to hold the sediments in place, erosion canrapidly carry away the soil.

18. In many parts of western New York State,the local bedrock is the sedimentary rockshale. Yet, metamorphic minerals such asgarnet are sometimes found in the soils ofthese areas. What do these exotic mineralstell us about the soils of New York State?

(1) Shale can also be a metamorphic rock.(2) Some soils are the result of frequent me­teor impacts. (3) The soils of these areaswere transported from the north. (4) Phys­ical weathering has turned clay into garnet.

19. The graph above shows four possible lineson a single set of axes. Which line best showshow the depth of a soil depends upon howlong it has been forming?

23. Which layer in this profile has the greatestpercentage of organic content? (1) A(2) B (3) C (4) D

100 Reviewing Earth Science

24. How did this soil originate? (1) erosion oforganic materials (2) weathering and bio­logical activity (3) melting followed bycrystallization (4) changed caused by heatand pressure deep within Earth

HOW ARE WEATHERED MATERIALSTRANSPORTED?

Rocks that have been broken into fragments, re­gardless of their size, are called sediments. Themineral composition or other characteristics ofsediments may be unrelated to the properties ofthe underlying bedrock. In such a case, the sedi­ments must have formed elsewhere and then

been transported from their place of origin. Ero­sion is the transportation of sediments mostoften by water, wind, or glaciers-the agents oferosion. These sediments are deposited in a dif­ferent location.

The force of gravity drives most forms of ero­sion. For example, weathering weakens a rockon a cliff. Gravity causes the weakened rock tofall to the bottom of the cliff. Piles of talus (bro­ken rock) accumulate at the bottom of a cliff.Continued erosion, perhaps helped by wind orwater, moves the sediment downslope, awayfrom the cliff.

Figure 4-7. This pile of rocks is the result of massmovement of the weathered rock of this cliff.

(ions) are carried in solution. Solution particlesare so small they cannot be filtered out of thewater. Sediments in suspension can be filteredout of the water. However, particles in suspen­sion are too small to settle on their own. The

flowing water rolls or bounces the largest andmost dense particles along the streambed. Parti­cles of low density, especially organic matter, arecarried along the surface by flotation.

The relationship of the size of the transportedparticle to water velocity is shown in Figure 4-8.The graph shows that the water velocity needed

Relationship of TransportedParticle Size to Water Velocity

100.0

~ ~9 p 01~ gj~ ~oa g-r.. (j1 a 08STREAM VELOCITY (cm/s)

Figure 4-8. There is a direct relationship between the

velocity of a stream and the size of the particles it can

transport. This generalized graph shows the water velocity

needed to maintain, but not start, movement of particles.

This graph can be found on page 6 of the Earth ScienceReference Tables.

Erosion by Gravity Acting AloneHave you ever seen rock debris that has fallenonto a road or to the bottom of a cliff as in Fig­ure 4-7? The downhill movement of rock or sed­

iment without being carried by water, wind, orice is known as mass movement, or mass wasting.Material can slide, flow, or fall to its resting place.Although the sediment is not really carried bywater, water in the sediment can act as a lubri­cating agent that makes mass movement morelikely. Alternate freezing and thawing also accel­erates this process. Mass movement includesslow creep, slumping, landslides, and even thefalling of individual rocks.

Erosion by WaterEach year, the streams and rivers of the worldcarry millions of tons of sediment downstreamand into the oceans. Running water, the mainagent of erosion in moist areas, transports sedi­ments in several ways. The smallest particles

E~a:wI-W

~ 0.115w

5 0.01i=a:«CI. 0.001

0.0001

Boulders

- - u - _"u u_ - _~ - - _n -. -- - n_ .--.2d.6.n - n __ u_

Cobbles- - - n_'_ - - - u.uu - - _. u __ - _. _._ 6.4- nn __ n

Pebbles

-- ---~_--.0.2. -- u - - u __

Sand

Silt

----. ---- ---.-------.- -----. 0.0004-~-------- u

Clay