Download Rocks and Landforms Investigation 3 Notes

ROCKS & LANDFORMS I-3 NOTES
Introduction
Physical Weathering
 Takes place over tens to hundreds of years
 Processes that take place in the surface
environment of the Earth
 Causes solid rock to be broken down into
loose pieces of minerals and rocks
Chemical Weathering
 Rocks from deep in the Earth (are at higher
temperature and pressure)
 When these rocks are brought near the
surface (different chemical environment). The
change in conditions makes some of the
minerals chemically unstable
 Some minerals may breakdown chemically
 Physical weathering and chemical weathering
act together. However, they will be studied
separately.
Physical Weathering
 Breaks rocks apart without changing their
mineral composition
Ice Wedging
 Water seeps into cracks in rocks
 Temp. drops, water freezes & expands
 The expansion puts enormous pressure on
the surrounding rocks
 Frozen water acts like a wedge, making
cracks wider
 After repeated freezing and thawing, the
rocks break apart.
 Expansion and contraction of water also
causes potholes in streets.
Plant Roots
 Plants take root in cracks of rocks
 Roots become larger and exert pressure
 Cracks in rocks become larger and rocks
break apart
Chemical Weathering
 Minerals in the rock dissolve in water forming
a weak acid (Acid Rain)
 Acidic water makes some rocks dissolve even
faster
 Rocks made of the mineral calcite (for
example, limestone, are most easily dissolved
by acidic water
 Without water, chemical reactions that
weather rocks happen slowly
Biological Processes in
Weathering
 Lichens
Lichens (continued)
 Among the first organisms that establish
themselves on bare rocks
 Produce a diluted acidic solution which break
down the minerals in rocks slowly
Weathering of the mineral
material in soil
 Microorganisms are present in the soil in
amazingly large numbers
 Larger animals, like earthworms and rodents
also live in the soil
 As plants and animals die, they add organic
material to the soil
 This organic material decays and is converted
into carbon dioxide
 Carbon dioxide forms more weak acid
(carbonic acid) promoting more weathering
The Earth Systems and
Weathering
Formation of karst landform
 Formed by chemical weathering
 Carbon dioxide is produced naturally by
animals, the use of fossil fuels and the decay
of organic matter in soil
 Some of this carbon dioxide is dissolved in
surface waters forming an acid
 In areas where pure limestone bedrock and
lots of rainfall, karst topography often
develops
 Happens both on rock surfaces and cracks
and fractures in limestone, as acidic
groundwater percolates downward
 Leads to large underground networks of
caverns
 Sometimes whole blocks of homes will
collapse, forming a sinkhole
Copy Chart
The
Atmosphere
The
Geosphere
The
Biosphere
The
Hydrosphere
 In boxes, write how karst topography occurs
in each of the four Earth Systems