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Discussion

Task 1. Read and memorize the following words:
encrust – утворювати тонкий шар acid - кислота
rupture - проривати, розривати blast - руйнувати
insulated –ізольований, роз’єднаний burrowing animals – ті тварини, що
риють і живуть у норах
frost wedging – розколювання гірської crevice - тріщина
породи під дією замерзаючих клинів
льоду (морозне вивітрювання)
fungus (fungi – мн.) - грибок exfoliation - сланцюватість,
листуватість, шарувата будова
arid - сухий, безводний; посушливий lichen ['laikən] - лишайник
salt crystal growth – збільшення sheeting - пласт, шар; утворення шарів,
кристалізації солей пластів
expansion - поширення на більшу spall off - дробити (породу) ;
поверхню розбивати (руду) ; обтісувати (камінь)
retain - зберігати spray - водяний пил

Task 2. Read the text. Translate it into Ukrainian. Talk about the main
types of mechanical weathering.
Mechanical Weathering
When a rock undergoes mechanical weathering, it is broken into smaller and
smaller pieces, each retaining the characteristics of the original material. The end result
is many small pieces from a single large one. In nature, four physical processes are
especially important in breaking rocks into smaller fragments: frost wedging, salt
crystal growth, expansion resulting from unloading, and biological activity.
Frost Wedging. If you leave a glass bottle of water in the freezer a bit too long,
you will find the bottle fractured. The bottle breaks because water has the unique
property of expanding about 9% upon freezing. This is also the reason that poorly
insulated or exposed water pipes rupture during frigid weather. You might expect this
same process to fracture rocks in nature. This is, in fact, the basis for the traditional
explanation of frost wedging.
Salt Crystal Growth. Another expansive force that can split rocks is created by
the growth of salt crystals. Rocky shorelines and arid regions are common settings for
this process. It begins when sea spray from breaking waves or salty groundwater
penetrates crevices and pore spaces in rock. As this water evaporates, salt crystals form.
As these crystals gradually grow larger, they weaken the rock by pushing apart the
surrounding grains or enlarging tiny cracks.
Sheeting. When large masses of igneous rock, particularly granite, are exposed
by erosion, concentric slabs begin to break loose. The process generating these
onionlike layers is called sheeting. It is thought that this occurs, at least in part, because
of the great reduction in pressure when the overlying rock is eroded away, a process
called unloading. Accompanying this unloading, the outer layers expand more than the
rock below and thus separate from the rock body. Continued weathering eventually
causes the slabs to separate and spall off, creating exfoliation domes.
Biological Activity. Both mechanical and chemical weathering are accomplished
by the activities of organisms. Plant roots in search of minerals and water grow into
fractures, and as the roots grow, they wedge the rock apart. Burrowing animals further
break down the rock by moving fresh material to the surface, where physical and
chemical processes can more effectively attack it. Of course, where rock has been

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