Relevant diagrams
Marjorie Henry, Contributor

In today's lesson I will conclude the discussion of Question 3 from the June 2008 examination paper. In the remaining section, Part (c), you must account for the formation of (i) waterfalls and (ii) deltas. Here is another example of where relevant diagrams can be used to help you answer the question. I cannot overstate that these must be done neatly and be well labelled.

Waterfalls

When rivers flow down a steep slope, the water may fall over a rock edge as a waterfall. Waterfalls are of two types:

(i) Those caused by differences in rock hardness into which the river is cutting.

(ii) Those caused by uplift of the land, lava flows and landslides.

When a layer of hard rock (rock which resists erosion) lies across a river's course, the soft rocks on the downstream side are more quickly eaten into than is the hard rock. The hard rock forms a steep edge over which the water falls. Gradually, the falling water digs out a deep pool at its base, called a plunge pool. The impact of the falling water (hydraulic action) undercuts the cliff edge until it collapses. This causes the waterfall to retreat upstream.

A waterfall develops when the hard rock layer is (i) horizontal (ii) dips gently upstream or (iii) is vertical.

Deltas

Most of the load carried by a river is ultimately dumped into the sea or lake into which it flows. The deposited load sometimes collects in the river mouth where it builds up into a low-lying swampy plain called a delta. Many deltas are near triangular in shape. Deltas are formed most easily under the following conditions:

• The river carries a large volume of sediment.
• The sea is relatively calm, so the sediment is not carried away by waves or strong currents.
• The sea is not too deep.
• The tidal range is not too great.

This concludes the question.

For those of you who are writing the external examinations this year, you would have already completed Paper 2 and are looking forward to Paper 1, the multiple-choice paper. Do not take this lightly. Remember you will be tested on all aspects of the syllabus, hence, there is the need to review all the material in much the same way as you did, hopefully, for Paper 2. As a means of emphasis, let me remind you of some of the guidelines in doing Paper 1.

(i) Read the STEM of the item carefully. Make sure that you understand it before attempting an answer. This can take different forms, namely, a question, a statement to be completed or several statements from which you must select what is true about a particular topic.

(ii) You are given four OPTIONS namely, A, B, C and D. Go through them quickly, yet carefully, so that you can identify the correct answer or KEY. It is not a guessing game.

(iii) Having made your correct selection, use a soft pencil to shade in the letter of that option on the answer sheet provided.

(iv) Expect some stimulus material on this paper. By now you should know that this includes maps, sketches, tables, diagrams, charts and graphs. The questions asked, of course, would be based on what is given.

(v) Time management is also important. Since there are 60 items to be done in one and a half hours, you have a minute and a half for each. Aim, however, at working through the answers within a minute and leave some time at the end to review your answers and to make corrections if necessary.

I wish that you will be successful in your examinations. Prepare well and remain focus.

Members of the George Washington Marching Band doing clean-up work inside the container which stores their band equipment at Linstead Primary and Junior High School, in St Catherine, on Labour Day, May 25. - Ricardo Makyn/Staff Photographer