Denudation This topic attempts to show how effective nature is at shaping the world around us. The physical landscape around us is very varied and in certain places it can be very beautiful and spectacular. When we look at or visit the "Grand Canyon", "Niagra Falls", the "Giant's Causeway" or the "Cliffs of Moher" we realise and appreciate this. Denudation is the term used to describe the constant on-going wearing down of the Earth's surface by Erosion, Weathering.
Denudation is the wearing away of the rocks on the earths surface Denudation occurs through 2 processes- 1. Weathering 2. Erosion Weathering: What is weathering? This is the break down and decay of rocks that are exposed on the earths surface to the weather Weathering takes place on site and material is not moved away Erosion: What is erosion? Breaking up of Rocks and removal of the rocks Erosion is caused by: moving water, ice and air Material that has been broken down is transported away and dumped somewhere else DENUDATION=EROSION + WEATHERING
There are 2 types of weathering: mechanical and chemical (1)MECHANICAL WEATHERING THIS OCCURS WHEN ROCKS ARE BROKEN DOWN INTO SMALLER PIECES. THIS IS CAUSED BY 1. FROST 2. SUDDEN CHANGES IN TEMPERATURES OR EXTREME TEMPERATURE CHANGES
MECHANICAL WEATHERING MECHANICAL WEATHERING OCCURS WHEN ROCKS ARE DISSOLVED BECAUSE OF A CHEMICAL CHANGE THIS IS USUALLY CAUSED BY WATER-RAIN
QUICK ACTIVITY WHAT IS MEANT BY THE TERM “DENUDATION” ? WHAT DO THE FOLLOWING TERMS MEAN (A) WEATHERING (B) EROSION NAME THE 2 TYPES OF WEATHERING NAME THE AGENTS THAT CAUSE EROSION NAME 2 DIFFERENCES BETWEEN WEATHERING AND EROSION
MECHANICAL WEATHERING NOW WE ARE GOING TO LOOK AT MECHANICAL WEATHERING: THERE ARE 2 TYPES OF MECHANICAL WEATHERING
1. Weathering. There are 3 types of mechanical weathering 3 TYPES OF Mechanical weathering 1.Freeze thaw action 2. Onion peeling exfoliation 3. Crystallisation of salts
Mechanical weathering: 1. Freeze Thaw Action (this occurs in upland areas) Freeze-Thaw Action During the day, water gathers in the cracks of rocks high up a mountain or in cold areas around the world. THIS WATER COMES FROM RAIN At night as temperatures drop, water freezes. it expands by 10% and as a result it exerts pressure on the surrounding rock. Over a period of time the rock breaks apart. Freeze- Thaw Action results in the accumulation of lots of small rocks known as "Scree“ gathering at the bottom on the slope.
Mechanical weathering 2.Exfoliation (Onion Peeling) Onion Peeling This process, also known as "Exfoliation", occurs in desert areas where there is a huge difference between the daytime and night time temperatures. The outer layer of the rock expands during the day due to the intense heat and contracts at night due to the extreme cold. This constant expansion and contraction weakens the rock and causes the outer layer to break away from the rock.
SUMMARY FREEZE THAW ACTION OCCURS IN UPLAND AREAS IT SHATTERS THE ROCKS INTO SMALLER PIECES CALLED SCREE THE SCREE GATHERS AT THE BOTTOM OF THE MOUNTAIN (AT THE FOOT OF THE SLOPES)
QUESTIONS What does freeze thaw action mean? What does scree mean? Draw a diagram to show how freeze thaw action occurs
Chemical weathering CARBONATION IS A TYPE OF CHEMICAL WEATHERING THAT WE WILL STUDY WHEN RAIN FALLS, IT TAKES IN CARBON DIOXIDE FROM THE ATMOSPHERE THE CARBON DIOXIDE MIXES WITH THE RAIN TO FORM CARBONIC ACID LIMESTONE ROCK CONTAINS CALCIUM CARBONATE (FROM ANIMAL BONES). WHEN THE ACID RAIN FALLS ON THE LIMESTONE, THE CARBONIC ACID REACTS WITH THE CALCIUM CARBONATE AND THE LIMESTONE IS DISSOLVED THERE ARE A LOT OF CRACKS IN LIMESTONE SO THIS MAKES IT EASY FOR THE RAIN TO PASS THROUGH IT
SWALLOW HOLES THE CARBONIC ACID IN RAIN DISSOLVES THE LIMESTONE. OVER TIME THE GRIKES (NOT YIKES) BECOME ENLARGED TO FORM SWALLOW HOLES WHEN THE RAINWATER DISAPPEARS UNDERGROUND, THE LIMESTONE IS DISSOLVED TO FORM LARGE CAVES
STALACTITES AND STALAGMITES STALACTITES DROPS OF WATER CONTAINING DISSOLFGVED LIMESTONE (CALCIUM CARBONATE) SEEP THROUGH THE ROCK SOME OF THESE HANG FROM THE ROOF OF THE CAVE. IF THE WATER EVAPORATES, IT LEAVES THE CALCITE BEHIND ON THE ROOF THESE GROW DOWN OVER THE YEARS TO FORM STALACTITES (HANG ON TITE) STALAGMITES IF THE DROPS OF WATER ON THE ROOF FALL TO THE FLOOR, THE WATER EVAPORATES LEAVING BEHIND CALCITE ON THE GROUND. OVER TIME THESE GROW TO FORM COLUMS CALLED STALAGMITES
Underground cave with stalactites and stalagmites
THE BURREN, CO CLARE THE BURREN IS ONE OF IRELANDS MOST IMPORTANT TOURIST DESTINATIONS. IT HAS A WIDE RANGE OF ATTRACTIONS FOR TOURISTS LIST 4 OF ITS MAIN ATTRACTIONS (PAGE 30) WHAT ARE 4 BENEFITS OF TOURISM IN THE BURREN? WHAT ARE 4 DISADVANTAGES OF TOURISM IN THE BURREN?