Working questions
Marjorie Henry, Contributor

Today, as promised, I will discuss question two from the June 2008 examination paper. I trust that you have the last lesson with the question.

(a)

(i) 309 landslides were recorded.

(ii) Intrusive igneous rocks had the highest number of landslides.

(iii) The number of landslides per kilometre on limestones is three.

(iv) The number of landslides that occurred on the rock type with the smallest area is 20.

(b)

(i) Landforms that are formed at plate boundaries are fold mountains; volcanic mountains and mid-oceanic ridges (any two responses would be correct).

(ii) At divergent margins, plates move away from each other and new material is added. These are also known as constructive plate margins. This new material is magma upwelling from the mantle.

At convergent margins plates are moving towards each other.

Plate material is being destroyed as one plate goes under (subducts) the other. These are also called destructive margins.

The subducting plate is melted as it goes back into the hot mantle.

The area of subduction is called the subduction zone.

(c)

The valley is V-shaped in the upper course of the river. In this section, the river valley is being deepened by vertical erosion. This is the dominant form of erosion in the upper course of the river. In the lower course, the shape of the valley is an open U shape. In this section, there is little erosion and deposition is dominant.

(d)

A spit is formed when a large accumulation of material forms a narrow strip of land that juts out into the sea, but is still connected to the mainland. Where a river carries large amounts of materials into a bay, waves moving obliquely will transport the material in a diagonal direction along the beach by the process of longshore drift. The spit may continue to grow, and if it joins on to an island or the mainland it becomes a feature known as a tombolo. Palisadoes in Jamaica is an example of a tombolo.

Fig. 1 (Source: General Geography In Diagrams - R. B. Bunnett)

Fig. 2 (Source: An Illustrated Dictionary of Geography - R. O. Buchanan)

(Source: Geography for CSEC - Jeanette Ottley et al)

Portmore Missionary Church's virtual school instructor, Bryan Case (right), attends to a patron. - Anthony Minott/Freelance Photographer