My Science School

The famous White Cliffs of Dover stand guard at the Gateway to England. Millions pass through Dover each year on their journey to or from the continent. In some places over 300 feet high, the White Cliffs are a symbol of the United Kingdom and a reassuring sight to travellers. The Cliffs have been immortalised in song, in literature and in art.

On a clear day you can see right across from the Dover cliffs to the cliffs on the French coast at Cap Gris Nez, proof of the continuous strata of chalk.

Around seventy million years ago this part of Britain was submerged by a shallow sea. The sea bottom was made of a white mud formed from the fragments of coccoliths, which were the skeletons of tiny algae which floated in the surface waters of the sea. This mud was later to become the chalk. It is thought that the chalk was deposited very slowly, probably only half a millimetre a year, equivalent to about 180 coccoliths piled one on top of another. In spite of this, up to 500 metres of chalk were deposited in places. The coccoliths are too small to be seen without a powerful microscope but if you look carefully you will find fossils of some of the larger inhabitants of the chalk sea such as sponges, shells, ammonites and urchins.

Since the time of the chalk sea, the chalk has been lifted out of the water by movements of the earth's crust. Most of the shaping of the beautiful chalk downlands we see today took place during the last Ice Age. The latter part of the Ice Age also saw the invasion of chalk by the English Channel. The consequence of this was that Britain became an island.

Credit : Dover Museum

Picture Credit : Google

The Grand Canyon attracts tourists because of its unique and intriguing geology. However, beyond its famous red and orange walls and winding crannies, it is a perfect white water rafting spot as well.

The Colorado River’s water levels through Grand Canyon are regulated every 9-12 hours and determined by the Colorado River Management Plan (CRMP). Big whitewater in Grand Canyon is not during spring run off like most other rivers as this river does not rely on the melting of the snow and ice for its water flow. Instead, white water rafting season in the Grand Canyon is generally during the warmer months when air conditioning becomes a necessity in the Southwest, and more water is needed downstream for agriculture. The more electricity needed in the surrounding states, Las Vegas for example, the more water is let down the river. The Glen Canyon Dam is responsible for producing this electricity and holding back the enormous amount of water collected at Lake Powell.

The commercial rafting season through Grand Canyon National Park operates from April through October. Each month has fluctuating water flows and every day the water is released within the predetermined water flow amount. These water levels are determined by the amount of moisture, snow melt and rain that the Upper and Lower Colorado River Basin receives. Once the amount of water is estimated, hydrologists determine the amount of water released on a monthly basis to meet the goals outlined in the CRMP. The water from the Colorado River is shared amongst 7 states and Mexico. The CRMP helps to meet the distribution goals and regulations in place to properly distribute the water amongst these areas. What does this mean for big whitewater in the Grand Canyon? It means that every year the water flows are different, and every month there is a team of scientists determining the amount of water that will be released downstream of Glen Canyon Dam.

Credit : Advantage

Picture Credit : Google