Rocks and sand on beaches become rounded rapidly because ________.
A) rip currents move the sand offshore rapidly, abrading the fragments
B) the swash action of waves rolls loose material up and down the beach, where it is
abraded rapidly to produce rounded grains
C) Beach sand is mostly calcium carbonate from reefs and so gets rounded easily
D) There is nothing particularly prominent in beaches that produces more rounding than
other sedimentary processes.
In much of what is now Canada, glaciers covered the land as little as 12,000 years ago
and glacial erosion scoured the land surface leaving very thin soil or bare rock over
large areas. The Midwestern United States was also covered in ice at this time, yet this
area contains some of the richest farm land in the world with thick soils. These soils are
formed on glacial sediments and windblown dust deposits from the ice age. Why are the
soil conditions between these areas so different when the soils are virtually identical in
age?
A) It is much colder in Canada so chemical weather is much slower; thus and soils have
not had time to form.
B) The Midwestern soils are transported soils with soil development on materials that
were already loose, unconsolidated materials.
C) Sea level rose following the ice age and covered the Midwest with an inland sea,
rapidly forming soil.
D) The Midwestern U.S. is much flatter than Canada, allowing soils to develop more
quickly.