Constructive and Destructive Processes Constructive Forces A A

Constructive and Destructive Processes

Constructive Forces A. A constructive force is on that build up the Earth’s surface. B. Examples: 1. Mountain building 2. Deposition of sediment n 3. Volcanic Eruption n

August 2006 brought two new things to the Tonga Islands in the South Pacific. One was a raft of lightweight, frothy volcanic rock—pumice— floating on the ocean surface. The other was a new island emerging out of the water.

Constructive Forces

Destructive Force A. A destructive force is one that destroys or breaks down the Earth’s surface. B. Examples: 1. Weathering- a process that causes the breakdown of rock. 2. Erosion- weathering and wearing away of rock into sediment. 3. Deforestation-clearing land of trees 4. Strip mining- clearing land to extract coal or other valuable minerals from the ground.

Destructive Forces- Deforestation n n Deforestation is brought about by the following: conversion of forests and woodlands to agricultural land to feed growing numbers of people; development of cash crops and cattle ranching, both of which earn money for tropical countries; commercial logging (which supplies the world market with woods such as meranti, teak, mahogany and ebony) destroys trees as well as opening up forests for agriculture; felling of trees for firewood and building material; the heavy lopping of foliage for fodder; and heavy browsing of saplings by domestic animals like goats.

CONSEQUENCES OF DEFORESTATION § Carbon Cycle: When forests are cleared, and the trees are either burnt or rot, this carbon is released as CO 2. This leads to an increase in the atmospheric CO 2 concentration. CO 2 is the major contributor to the greenhouse effect. § Water Cycle: With removal of part of the forest, the region cannot hold as much water. The effect of this could be a drier climate. § Soil erosion: With the loss of a protective cover of vegetation more soil is lost. § Silting of water courses, lakes and dams: This occurs as a result of soil erosion. § Extinction of species: which depend on the forest for survival. Forests contain more than half of all species on our planet - as the habitat of these species is destroyed, so the number of species declines. § Desertification: The causes of desertification are complex, but deforestation is one of the contributing factors.

Weathering and Erosion

Strip Mining

Deforestation