Weathering, Limestone and erosion Flashcards
What is weathering
WEATHERING IS THE BREAKING DOWN OR
DISSOLVING OF ROCKS AND MINERALS ON
EARTH’S SURFACE.
What is erosion
EROSION IS THE GEOLOGICAL PROCESS IN
WHICH EARTHEN MATERIALS ARE WORN
AWAY AND TRANSPORTED BY NATURAL
FORCES SUCH AS WIND OR WATER.
what is the difference between weathering and erosion
Erosion is the displacement (movement from one place to another) of solids by wind, water and ice. weathering is the decomposition of rocks, soil and minerals by direct contact with atmospheric pressure such as air pressure. With erosion there is displacement and with weathering there is no displacement. The different types of erosion are wind, water and ice. The different types of weathering are physical, chemical and biological weathering.
LIMESTONE
A HARD SEDIMENTARY ROCK, COMPOSED MAINLY OF CALCIUM
CARBONATE OR DOLOMITE, USED AS BUILDING MATERIAL AND IN
THE MAKING OF CEMENT.
3 TYPES OF LIMESTONE ROCKS
Travertine, Oolitic limestone, Fossiliferous
CHARACTERISTICS OF LIMESTONE ROCK
LIMESTONE ROCKS ARE COMMONLY COMPOSED OF TINY
FOSSILS, SHELL FRAGMENTS AND OTHER FOSSILIZED
DEBRIS. THESE FOSSILS ARE FREQUENTLY VISIBLE TO
THE UNAIDED EYE ON CLOSE EXAMINATION OF THE
STONE SURFACE, HOWEVER THIS IS NOT ALWAYS THE
CASE.
SOME VARIETIES OF LIMESTONE HAVE AN EXTREMELY
FINE GRAIN.
LIMESTONE IS USUALLY GRAY, BUT IT MAY ALSO BE
WHITE, YELLOW OR BROWN. IT IS A SOFT ROCK AND IS
EASILY SCRATCHED. IT WILL EFFERVESCE READILY IN
ANY COMMON ACID.
IT HAS BEEN FOUND THAT ALL LIMESTONES ARE
CRYSTALLINE BUT WITH VARYING CRYSTAL SIZES,
UNIT FORMITY, AND CRYSTAL ARRANGEMENT
LIMESTONE IS A HARD ROCK AND PERMEABLE ONE. THIS
MEANS IT ALLOWS WATER TO PASS THROUGH
(PERCOLATE) IT
THE CHEMICAL COMPOSITION OF LIMESTONE ROCK
LIMESTONE IS MADE UP OF VARYING PROPORTIONS OF THE FOLLOWING CHEMICALS WITH CALCIUM AND MAGNESIUM CARBONATE BEING THE TWO MAJOR COMPONENTS
(Calcium carbonate) CaCO3 + (Alumina) Al2O3 = (Monocalcium aluminate) CaAl2O4 (2
HOW ARE LIMESTONES FORMED
LIMESTONE IS FORMED IN TWO WAYS. IT CAN BE
FORMED WITH THE HELP OF LIVING ORGANISMS AND
BY EVAPORATION.
THE SECOND WAY LIMESTONE IS FORMED IS WHEN
WATER CONTAINING PARTICLES OF CALCIUM
CARBONATE EVAPORATE, LEAVING BEHIND THE
SEDIMENT DEPOSIT. THE WATER PRESSURE COMPACTS
THE SEDIMENT, CREATING LIMESTONE.
OCEAN-DWELLING ORGANISMS SUCH AS OYSTERS,
CLAMS, MUSSELS AND CORAL USE CALCIUM
CARBONATE (CACO3) FOUND IN SEAWATER TO
CREATE THEIR SHELLS AND BONES. AS THESE
ORGANISMS DIE, THEIR SHELLS AND BONES ARE
BROKEN DOWN BY WAVES AND SETTLE ON THE
OCEAN FLOOR WHERE THEY ARE COMPACTED OVER
MILLIONS OF YEARS, CREATING LIMESTONE FROM THE
SEDIMENTS AND THE PRESSURE OF THE OCEAN
WATER.
Types of surface and underground limestone features
SURFACE FEATURES
Limestone pavements - Flat areas of exposed limestone….Resemble artificial pavements…Comprise large rectangular blocks called clints…separated by long grooves known as grikes A result of chemical weathering along the joints and cracks in the limestone rocks…The grikes will deepen and widen over time
Sinkholes - A sinkhole is a hole in the ground that forms when water dissolves surface rock. Often, this surface rock is limestone, which is easily eroded, or worn away, by the movement of water.
Dry Valleys - During the last ice age the limestone was frozen to great depths. When the ice melted it carved out valleys over the frozen rock. When the limestone thawed out the surface water was able to infiltrate down through the rocks and the dry valleys were left with no surface water.
George
Spring
Bedding Plane
UNDERGROUND FEATURES
Stalactites - Water dripping from the ceiling of a cave contains dissolved calcium carbonate. Some of this calcium carbonate may be deposited on the ceiling of the cave. Over time the deposition of calcium carbonate will form an elongated feature which hangs down from the ceiling.
Stalagmites - As water drips from the ceiling onto the floor of the cave, calcium carbonate may be deposited on the floor of the cave. Over time this may form an elongated feature which rises vertically from the cave floor. This feature is known as a stalagmite.
Note: A simple way to avoid confusion is to remember that stalactite has a “c” for “ceiling” and stalagmite has a “g” for “ground”.
Pillar - A stalagmite may form directly below a stalactite as water drips from the ceiling of the cave onto the floor. The stalactite may continue to grow downwards and the stalagmite may continue to grow upwards until the two limestone features eventually meet. When this happens they form a new feature known as a pillar or column which extends all the way from the ceiling of the cave to the floor.
Cavern
Limestone Landscape
A limestone region characterised by sinkholes and
caves is known as karst
It is formed by the chemical weathering (carbonation
and solution) of limestone rocks
Karst system
When rainwater reacts with carbon dioxide in the air or
in the soil, it forms carbonic acid
The acid changes the calcium carbonate in limestone to
calcium bicarbonate which dissolves in water
This process results in the formation of karst features
on the surface and beneath it
Chapter 15: Limestone Environment
Importance of understanding karst systems
Karst landscapes make up about 10% of the Earth’s
surface
They are most abundant in tropical humid regions but
also occur in temperate, tropical, alpine and polar
environments
A quarter of the world’s population depend on water
supplied from karst areas
However, karst systems are vulnerable to groundwater
pollution due to the relatively rapid water flow and the
lack of a natural filtration system
Local drinking water supplies risk being contaminated
as a result
