- Education and Science»
- Geography, Nature & Weather
What is Sand? Formation, Beaches, Composition and Uses
Sand is composed of loose pieces of rocks, minerals and soil particles. Sand is found in beaches, lakes, rivers, bottom of oceans and desserts.
The constant weathering of land forms such as mountains and hills by natural forces such as rain, wind and ice over millions of years has lead to the formation of sand.
Sand is granular in texture. An individual particle of sand is called a grain. Grains of sand can be rounded or angular in shape.They range from 1.6 mm to 2 mm in size.The color of the sand grains depends upon the geographical location and the environmental conditions of the surrounding place.
Formation of sand
Sand formation starts when a landmass breaks down to form rocks. These rocks are further broken down into smaller and smaller pieces by nature's forces to form sand. Sand formation through natural forces can take anywhere from hundreds to millions of years.
The breaking down of rocks into smaller pieces by forces of nature is called weathering. Sand is the result of mechanical, chemical and biological weathering that has occurred for over million of years.
Mechanical weathering is weathering that occurs due to the forces of the wind, water and extreme changes in temperature. Rainwater that seeps into cracks and crevices of rocks turns into ice when the temperature falls below zero degrees centigrade.
When the surrounding temperature increases the ice thaws. Over time, the freezing and thawing process causes the rocks to break apart into smaller pieces. These smaller pieces are broken into more tiny pieces to form grains of sand.
In deserts, there are extreme changes in temperatures. During the day, the temperatures are very high and in the night, it becomes very cold. The constant heating and cooling of rocks weaken them and over time they break down into smaller fragments.
Mechanical weathering also occurs when the strong winds constantly hit against rocks and boulders causing them to break apart.
Roots of trees growing in the sides of mountains penetrate deep and cause cracks in the rocks. These cracks become wider when the rainwater collects and freezes to form ice.
Chemical weathering weakens the rocks and aids in the process of disintegration through chemical reactions.
Water combines with carbon dioxide and forms carbonic acid; this carbonic acid dissolves the rocks causing them to weaken and break down. Temperature and moisture play an important role in chemical weathering.
Biological weathering is weathering that occurs due to the activity of plants and animals.
For example, lichens release chemicals that weaken the rocks. These weakened rocks can easily be broken down by forces of nature into smaller pieces.
Roots of trees that grow on the mountainside can cause cracks to develop in the rocks, this can be considered as biological weathering because it is caused by the growth of the plant roots.
Formation of sand is the result of all three types of weathering - mechanical, chemical and biological weathering.
Composition of Sand
The composition of sand depends on the rocks present in the region and environmental conditions of the place. The color of sand depends on what the sand is made of and varies according to the composition.
Beach sand is made up of pebbles, shells, and small stones. Most of the beaches around the world are made of minerals like quartz and feldspar.
Quartz is made from silicon dioxide and Feldspar is made of sodium, calcium, or potassium along with quartz.
Quartz is found in abundance in beaches because they are hard and can survive weathering. Quartz can be broken down into smaller pieces but they do not easily dissolve and disappear because they are strong and resistant to chemical reactions.
Other than calcium and feldspar mica flakes can also be seen in beach sands.
The color of sand depends on what the sand is made of and varies according to the composition.
Presenting different colored sands around the world -
Black Sand Beaches
Black sand beaches are composed of volcanic minerals and lava fragments. These beaches are black in color because the volcanic minerals and rocks are in hues and shades of the color, black.
The minerals that give the dark color to the sand are pyroxenes, amphiboles, and iron oxides. Black sands are heavier than the light brown colored sand and become very hot on a sunny day.
Many black sand beaches are found in Hawaii - Pololu Valley Beach and Kehena Beach, Honokalani Black Sand Beach
Other Black Sand Beaches - Vik Beach in Iceland, Prince William Sound, Alaska.
The White Sands National Monument in New Mexico
The White Sands National Monument in New Mexico has about 275 square miles of white sand dunes that are made of gypsum that has been broken down over millions of years. The broken down Gypsum gives the white color to the sand.
According to the New Mexico New Port, a student journalism lab at the University of New Mexico the white sands are the remnants of a lake called Lake Lucero that existed a million of years ago.
Gypsum was produced at a faster rate than the water in the lake could dissolve and due to this reason layers of gypsum were left behind as the water evaporated.
The force of wind broke down large pieces of Gypsum into Selenite (broken down pieces of Gypsum are known as Selenite).
The original Selenite that was formed had a clear surface but over time, Selenite was eroded by the wind and developed many cracks. It is the reflection of light through these cracks that makes the sand look white.
Other white sand beaches around the world – White Beach Boracay in the Philippines, The Maldives in the Indian Ocean, Wine Glass Bay in Tasmania, Grand Anse Beach in Seychelles.
Papakolea Green Sand Beach
Papakolea Green Sand Beach also known as Puu Mahana Beach in Big Island, Hawaii is surrounded by cliffs that are olive green in color. The sand on the beach is due to constant erosion of a volcanic cinder cone called Diamond Head in Oahu, close to the beach.
The sand is composed of basaltic lava that is rich in a mineral called Olivine. Olivine is green in color and lends the shade of green to the sand.
Red Sand Beaches
Red sand beaches can be found in Hawaii, USA, Rabida Island, Galapagos and Santorini, Greece.
The sands in Rabida Island Galapagos is red due to the oxidation of iron-rich lava deposits and coral sediments that have been washed ashore.
The red color of the Red Sand Beach in Santorini is due to the erosion of the surrounding cliffs that are made of red color sedimentary rocks.
Kaihalulu Beach sand in Hawaii is blackish- red in color because of the erosion of the cinder cone called Ka’uiki Head on the Northern end of the cove.
Uses of Sand
Sand is an important component of building materials such as mortar, cement, asphalt, paving, plaster and concrete. Sand is added to building materials to make them harder to bear more weight.
Pure quartz sand is used in pottery and glass making industries, to line the hearth of acid-steel furnaces because quartz sand can withstand high temperatures.
Sand is also used for the following -
- as a filter to purify water
- glued to paper to make sand paper
- it is used as a sandblast to clean walls of buildings
Sand is formed by erosion of land masses over millions of years. The composition of sand depends upon the place where it is found. Sand has many uses and plays a significant role in the construction industry.