Weathering is the process where rock is dissolved, worn away or broken down into smaller and smaller pieces. There are mechanical, chemical, and organic weathering processes.
Weathering process are primarily responsible for soil development. These process take thousands of years. Climate, vegetation, and rock type determine what type of soil forms. Soil contains organic matter from decaying plants and animals (humus) as well as sand, silt, and clay. It covers the landscape and provides a medium for plants to grow.
Weathering is caused by water, as it freezes and melt, as well as by chemical reactions that loosen the bonds holding rocks together.
1. Organic weathering happens when plants break up rocks with their growing roots or plant acids help dissolve rock.
2. Mechanical weathering physically breaks up rock. One example is called frost action or frost destroying. Water gets into craks and joints in bedrock. When the water freezes it expands and the cracks are opnened a little wider. Over time pieces of rock can split off a rock face and big boulders are broken into smaller rocks and gravel. This process can also break up bricks on buildings.
3. Chemical weathering decomposes or decays rocks and minerals. An example of chemical wethering is water dissolving limestone.
Once the rock has been weakened and broken up by weathering it is ready for erosion. Erosion happens when rocks and sediments are picked up and moved to another place by ice, water, wind, or gravity.
Erosion in Wet Climate
As soon as rock is exposed on the earth's surface, it is attacked by wind, water, or ice - a process known as "weathering". This prepares for erosion, when rock is broken down and removed. Weathering can be either physical (wearing away the rock itself) or chemical (attacking the minerals in the rock). Climate and rock type determine the kind of weathering that occurs. In wet climates, chemical weathering, mainly by rainwater, is dominant.
Mountain Stream
Cascading over steep gradients, a swift-flowing stream wears away softer rocks. Harder rocks remain and create rocky outcrops. These become steep rapids or waterfalls.
Frost Shattering
This type of weathering occurs when water in cracks in the rock freezes and expands. Joints in the rock widen and the rock shatter
Clints and Grikes
Acid in rainwater seeps into limestone joints and dissolves the calcite in the rock. Ridges known as "clints" and grooves known as "grikes" form in the rock.
Erosion in Arid Climate
In hot, dry, desert areas extremes of temperature cause rocks to fragment. By day, rock expands in the heat, and by night it contracts in the cold. It is mainly physical weathering that occurs in arid (dry) climate, chiefly caused by wind helps to erode rocks and build shifting sand dunes.
Onion-skin layering
In the heat of the desert, a rock's surface may expand, though the interior stay cool. At night, the surface of the rock cools and contracts. This daily process causes flaking on the surface of the rock, and the outer layers begin to peel and fall away.
Zeugens
Sand carried by the wind sculpts these strange forms called "zeugens". Sand wears away soft rock leaving behind areas of harder rock, worn into jagged shapes.
Mushroom rocks (Pedestal rocks)
The desert wind contains a great deal of sand, which scours away the surface of rocks. Mushroom-shaped rocks are a result of this action. Rocks are worn away most at their base by the sand, leaving behind a landscape of rock pedestals.
An earthquake is what happens when two blocks or plate or the earth suddenly slip past one another. The surface where they slip is calledfault plane. The location below the earth's surface where the earthquake starts is called hypocenter, and the location directly above it on the surface of the earth is called epicenter.
More than a million times a year, the earth's crust suddenly shakes during an earthquake. Most of the world's earthquakes are fairly slight. A mild earthquake can feel like a truck passing, it can destroy roads and buildings, and also cause the sea to rise in huge waves.
Earthquakes often happen near volcanoes and young mountain ranges: at the ridges of the earth's plates.
What causes earthquakes and where do they happen?
The earth has four major layers: the inner core, outer core, mantle, and crust. The crust and the top of the mantle make up a thin skin on the surface of our planet. But this skin is not all in one piece, it is made up of many pieces like a puzzle covering the surface of the earth. Not only that, but these puzzle pieces keep slowly moving aroung, sliding past one another and bumping into each other, we called it as a tectonic plates and the edge of the plates are called the plate boundaries. The plate boundaries are made up of many faults, and most of the earthquakes around the world occur on these faults. Since the edges of the plates are rough, they get stuck while the rest of the plate keep moving. Finally, when the plate has moved far enough, the edges unstick on one of the faults and there is an earthquake.
Earthquakes are caused by disturbances in the interior of the earth and other causes.
Tectonic Movements: The disturbances inside the earth are called tectonic movements.These forces bring about changes on the earth surface and physical features like mountains, plateaus and rift valleys are formed.Most disastrous earthquakes are caused by tectonic forces .Tectonic forces create tension and pressure and the stress begins to build up inside the earth. When the stress tends to be more than what the rocks of the earth can bear, the rocks are broken and displaced from their state of equilibrium. It is known as faulting. The energy accumulated during faulting is released.This release of energy gives rise to mighty waves.These waves originate from a point called Focus in the interior of the earth and then spread out in all directions.On the surface whatever comes into their contact begins to vibrate.The chief cause of earthquakes felt often in California in USA is often the San Andreas Fault found there.
Volcanic Eruptions:The volcanic eruptions are often very violent and cause vibrations in the earth crust. Sometimes the vent of a volcano is blocked temporarily and explosive eruption takes place suddenly causing tremors in the earth crust.The Krakatoa that erupted in 1883 became the cause of a violent earthquake there.
Other Reasons:The roofs of underground caves sometimes give way and release great force to cause minor tremors in the earth crust. Nuclear explosions also release massive energy to cause tremors in the earth crust.
Why does the earth shake when there is an earthquake?
While the edges of faults are stuck together, and the rest of the block is moving, the energy that would normally cause the blocks to slide past one another is being stored up. When the force of the moving blocks finally overcomes the friction of the sharp edges of the faults and it unsticks, all that stored up energy is released. The energy radiates outward from the fault in all directions in the form of seismic waves like ripples on a pond. The seismic waves shake the earth as they move through it, and when the waves reach the earth's surface, they shake the ground and anything on it, like our houses and us.
How are earthquakes recorded?
Earthquakes are recorded by instruments called seismograph. The recording they make is called a seismogram. The seismograph has a base that sets firmly in the ground, and a heavy weight that hangs free. When an earthquake causes the ground to shake, the base of the seismograph shakes to, but the hanging weight does not. Instead the spring or string that it is hanging from absorbs all the movement. The difference in position between the shaking part of the seismograph and the motionless part is what is recorded.
A short curving line that doesn't curve very much means a small earthquake, and a long curving line that curve a lot means a large earthquake. The length of curve depends on the size of the fault, and the size of the curve depends on the amount of slip.
Earthquake Damage
In general, great loss of life during an earthquake can be avoided. It is often not the earth's shaking that kills people, but falling buildings, particulary poorly constructed ones. Landslides and tsunami is also cause a lot of damage. During an average earthquake, it is best to stay indoor in a doorway or under sturdy table.
Fire poses a great danger following an earthquake. Gas leaks and oli spills can lead to large fires. Loose rock and debris may be dislodged by an earthquake and cause landslides. Landslide too may be triggered by the ground shaking. Mudflows, or lahars, can result from rain or snow mixing with loosened soil.
Effects of Earthquakes
Earthquakes are less advantageous and more harmful to human. Damage done is chiefly in following respects:
Loss of Property: Severe earthquakes reduce to rubble human structures ranging from huts to palaces and single storey to multi storey buildings.Even pipelines laid under the ground and railway lines are damaged or displaced.The best example of this type of damage is Koyana earthquake in 1970.
Loss of Life: Earthquake tremors of a few seconds takes the lives of thousands of people. Many people have been rendered homeless or suffered injuries in various ways.
Changes in the path of rivers: On account of the impact of earthquakes,sometimes rivers also change their path.Consequently, when floods come they play chaos with people's lives.
Tsunami:The earthquakes in the sea generate massive waves called Tsunami in Japanese language.It sometimes rises to the height of 20-25 metres. It causes great damage to life and property of people living in coastal areas as well as to tourists.Tsunami caused by an earthquake in the sea near Sumatra on 26th Dec,2004 hit south east Asian countries including India and Sri Lanka.There was heavy damage in these countries.
Mud Fountains: On account of earthquakes of high intensity,warm water and mud fountains also burst.
Cracks in Earth Crust: Earthquake cause cracks in earth's crust anywhere in fields,roads,parks and even hills.They are thus rendered useless.The San Andreas fault in California ,U.S.A. was created in a similar manner.
What is a tsunami?
A tsunami is a large ocean wave usually caused by an underwater earthquake or a volcanic explosion. Tsunamis are not tidal waves. Tidal waves are caused by the forces of the moon, sun, and planets upon the tides, as well as the wind as it moves over the water. With typical waves, water flows in circles, but with a tsunami, water flows straight. This is why tsunami cause so much damage!
Most volcanoes are found at plate boundaries near the Pacific coast or at mid-ocean ridges. Here, fractures in the litosphere allow molten rock, called "magma", to rise from the mantle inside the Earth. Magma is known as "lava" when it flows out of a volcano. Ash, steam, and gas also spew out from a volcano and can cause a great deal of destruction.
In general, volcanoes, like earthquakes, occur near plate boundaries. Volcanoes are formed by plate destruction or the presence of a hot spot underneath the plate. Volcanoes are formed when magma from within the Earth's upper mantle works its way to the surface. At the surface, it erupts to form lava flows and ash deposits. Over time as the volcano continues to erupt, it will get bigger and bigger.
The Earth's crust is made up of huge slabs called plates, which fit together like a jigsaw puzzle. These plates sometimes move. The friction causes earthquakes and volcanic eruptions near the edges of the plates. The theory that explains this process is called plate tectonics.
Plate Tectonic
The theory of plate tectonics is a interesting story of continents drifting from place to place breaking apart, colliding, and grinding against each other. The plate tectonic theory is supported by a wide range of evidence that considers the earth's crust and upper mantle to be composed of several large, thin, relatively rigid plates that move relative to one another. The plates are all moving in different directions and at different speeds. Sometimes the plates crash together, pull apart or sideswipe each other. When this happens, it commonly results in earthquakes.
There are more than 1500 active volcanoes on the Earth. We currently know of 80 or more which are under the oceans.
Type of Volcanoes
Volcanoes are grouped into four types: cinder cones, composite volcanoes, shield volcanoes and lava volcanoes.
Cinder Cones
Cinder cones are circular or oval cones made up of small fragments of lava from a single vent that have been blown into the air, cooled and fallen around the vent.
Composite Volcanoes
Composite volcanoes are steep-sided volcanoes composed of many layers of volcanic rocks, usually made from high-viscosity lava, ash and rock debris. Mt. Rainier and Mount St. Helens are examples of this type of volcano.
Shield Volcanoes
Shield volcanoes are volcanoes shaped like a bowl or shield in the middle with long gentle slopes made by basaltic lava flows. Basalt lava flows from these volcanoes are called flood basalts. The volcanoes that formed the basalt of the Columbia Plateau were shield volcanoes.
Lava Volcanoes
Lava domes are formed when erupting lava is too thick to flow and makes a steep-sided mound as the lava piles up near the volcanic vent. The eruption of Mount St. Helens in 1980 was caused in part by a lava dome shifting to allow explosive gas and steam to escape from inside the mountain.
Sometimes volcanoes explode violently. Volcanoes that form from viscous lava are most likely to do this. Viscous lava tends to plug up volcanic vents. When pressure in the magma chamber increase, the lava is blown out. Pieces of rock and a great deal of ash are hurled high into the air. Clouds of ash and pumice flow like hot avalanches down the sides of the volcano. Mudflows (also called "lahars") are mixture of water and ash. They travel at great speed and engulf everything in their paths.
Product of explosive volcanoes: 1. Ash : Lava particles larger than dust cover the land
2. Lapili: Lava ejected in pea-sized pieces. 3. Pumice: Light-weight lava filled with holes 4. Bomb: Bomb-shaped lava forms as it flies in the air
5. Pele's hair: Sometimes drops of liquid lava blow into fine spiky strands. The threads form needles of volcanic glass. They are named Pele's hair after Pele, the Hawaiian goddess of volcanoes.
The Effect of Volcanoes Eruption to The Landscape of Environment
Movement in rocks underground can cause changes to the landscape above. The combination of heat and water in the Earth's rocks produce various phenomena. Molten rock erupting out of the Earth brings gases, mineral deposits, and water with it. Mud pools, hot springs, and geysers from when the gases and water escape. Mineral dissolved in the hot waters precipitate to form cone-like or terraced deposits of rocks.
The landscape around volcanoes: 1. Hot springs : Magma warms water in cracks in the rocks. Water returns to the surface as a hot spring.Occur where the water temperature is below the boiling point. 2. Mud pools: Steam, particles of rock, and vulcanic gases bubble through pools of liquid mud. 3. Fumaroles: Vents, or fumeroles, allow steam and other gases to escape from colling rocks. 4. Geysers: Heat from magma chambers causes ground water to boil, erupting as jets of steam and water. For geyser to occur there must be heat, water, and a plumbing system. A magma chamber provides the heat, which radiates into surrounding rock. Water from rain and snow works its way underground through fractures in the rock.
As the water reaches hot rock it begins to rise back to the surface, passing through rhyolite, which is former volcanis ash or lava rich in silica. The hot water dissolves the silica and carries it upward to line rock crack. This forms a constriction that holds in the mountain pressure, creating a geyser's plumbing system.
5. Terraces: Minerals, dissolved in heated ground water, are deposited in layers that rise around vent.
