Weathering Flashcards
What is weathering?
Weathering – means the physical and chemical processes that break rocks down. Rocks do not last forever because weathering breaks them down into smaller pieces.
What is physical weathering is caused by?
Physical weathering can happen because of:
* Temperature change – Solids expand when they are heated and contract when they are cooled. If the temperature change is very quick, this can cause the rock to crack.
* The action of water and ice – Ice can split rocks by cooling them rapidly. Ice also widens cracks in rocks. This is because any water that enters the rock will expand and freeze. Water running or washing over the rock can also gradually wear away rock material.
- Crystallisation of salts – Water often contains dissolved chemicals in it called salt. Salts can form crystals inside the rock which will cause tremendous pressure which will cause pieces to snap off.
- Wind – Fine particles of rock carried by wind can blast the rock surface wearing pieces away.
- Living plants – A plant can grow through cracks of a rock which will expand it and make more cracks.
What is chemical weathering caused by?
Chemical weathering can happen because of:
* Gases – A certain gas can react with a certain type of rock. Gases reacting with rocks can cause the rock to crumble and lose colour.
* Acids – Rain water dilute acids that can attack the rock. These acids naturally form in the aur during lightning. Pollution also forms acid in the air. This is known as acid rain.
* Water – Some rocks have soluble materials in them. This means that they could be dissolved because of water which removes cement that holds the rock in place which will cause it to crumble.
What is erosion?
Erosion - Small particles of rock that has been broken off from another rock because of weathering can be carried away by water, wind and ice. This removal of small rock particles is erosion. The water, wind and ice are agents of erosion.
What is deposition?
Deposition – The small rock particles that are carried away from the weathered rock are eventually dropped off somewhere. The process of depositing eroded rock particles is called deposition or sedimentation. Deposition occurs where the mocing water, wind or ice that is carrying the rock particles slows down. In rivers this slowing down occurs at bends and where rivers leave mountains and enter plains.
