Mountain & Erosion

MOUNTAIN & EROSION PREPARED BY; GROUP 5 ALIF INDRA JAMUNAH

WHAT IS A MOUNTAIN?  A mountain is a landform that extends above the surrounding terrain in a limited area.  A mountain is generally higher and steeper than a hill, but there is considerable overlap, and usage often depends on local custom.

 Mountains cover 54% of Asia, 36% of North America, 25% of Europe, 22% of South America, 17% of Australia, and 3% of Africa.  As a whole, 24% of the Earth's land mass is mountainous  Also, 1 in 10 people live in mountainous regions.  Mountains are generally given as heights above mean sea level.  The highest mountain on Earth is Everest, 8,848 m, set in the world's most significant mountain range, the Himalaya

 Everest is the highest elevation on land, but it is only a single peak in an entire mountain range.  Mauna Loa is a single mountain on the island of Hawaii. The island of Hawaii is actually an island made up of five volcanoes which "blend" together because of their closeness to each other, making a single island.  Mauna Loa takes up a lot of space because its mass is 9,700 cubic miles/40,000 cu km of mountain.

Mauna Loa is a volcano, just like many others found on the island chain Mauna Loa is one of many shield volcanoes that make up the Hawaiian Islands. These are volcanoes that, compared to their more violent companions, erupt slowly and quietly. The study of mountains, Orology is a specialized branch of Geology There are used to describe mountainous areas and things associated with them

CHARACTERISTICS  Located close to the Earth's poles, reach into the colder layers of the atmosphere  Have very different climatic conditions at the top than at the base  Have different life zones at different altitudes  Generally less preferable for human habitation than lowlands

 The weather is often harsher  At very high altitudes, there is less oxygen in the air and less protection against solar radiation (UV).  Acute mountain sickness (caused by hypoxia - a lack of oxygen in the blood) affects over half of lowlanders who spend more than a few hours above 3,500 meters (11,483 feet).  A mountain is usually produced by the movement of lithospheric plates, either orogenic movement or epeirogenic movement.

 Two types of mountain are formed depending on how the rock reacts to the tectonic forces – block mountains or fold mountains.  Some isolated mountains were produced by volcanoes, including many apparently small islands that reach a great height above the ocean floor.

WHAT IS AN EROSION?  Soil erosion is a natural process. It becomes a problem when human activity causes it to occur much faster than under natural conditions

FACTORS AFFECTING EROSION Natural factors  heavy rains on weak soil: rain drops loosen soil particles and water transports them down hill.  vegetation depleted by drought: rain drops are free to hit the soil, causing erosion during rainfall. Winds blow away the fine particles during droughts.

 steep slopes: gravity 'pulls harder': water flows faster; soil creeps, slips or slumps downhill.  sudden climate change – rainfall: erosion increases unexpectedly rapidly as rainstorms become more severe. – drought: water dries up and the soil becomes a playball of winds. Soil biota die. A sudden rain causes enormous damage. – changing winds: areas previously sheltered, become exposed.

Human-induced factors  change of land (deforestation): the land loses its cover, then its soil biota, porosity and moisture.  intensive farming: the plough, excessive fertiliser and irrigation damage the land, often permanently.  housing development: soil is bared; massive earthworks to landscape the subdivision; soil is on the loose.  road construction: roads are cut; massive earthworks, leaving scars behind. Not enough attention paid to rainwater flow and maintenance of road sides.

 Rain has been recognised as one of the most influential factors on soil erosion as it transports soil away, visible by rivers becoming streams of mud.  But the damage caused by rain drops hitting the soil, has been recognised only recently. When soils dry out, wind can transport soil particles as dust storms. Also frost can be damaging to soils.

 Wind and water are the main agents of soil erosion. The amount of soil they can carry away is influenced by two related factors: * speed - the faster either moves, the more soil it can erode; * plant cover - plants protect the soil and in their absence wind and water can do much more damage

THE IMPORTANCE OF PLANTS  Plants provide protective cover on the land and prevent soil erosion for the following reasons:  * plants slow down water as it flows over the land (runoff) and this allows much of the rain to soak into the ground;  * plant roots hold the soil in position and prevent it from being washed away;

 * plants break the impact of a raindrop before it hits the soil, thus reducing its ability to erode;  * plants in wetlands and on the banks of rivers are of particular importance as they slow down the flow of the water and their roots bind the soil, thus preventing erosion.

PREVENTING SOIL EROSION Political and economic changes need to address the distribution of land in South Africa as well as the possibility of incentives to encourage farmers to manage their land sustainably.  Aspects of technical changes include:  * the use of contour ploughing and wind breaks;  * leaving unploughed grass strips between ploughed land;

 * making sure that there are always plants growing on the soil, and that the soil is rich in humus (decaying plant and animal remains). This organic matter is the "glue" that binds the soil particles together and plays an important part in preventing erosion;  * avoiding overgrazing and the over-use of crop lands;

 * allowing indigenous plants to grow along the river banks instead of ploughing and planting crops right up to the water's edge;  * encouraging biological diversity by planting several different types of plants together;  * conservation of wetlands (see Enviro Facts "Wetlands" and "River Catchments").

THE END

THANK YOU