Question

A coal seam occurs in a stratigraphic sequence as shown in the figure. If a vertical borehole is drilled at location B, the coal seam will be intersected at a depth (in m) of ........ 

Hint:

To determine the depth of a dipping layer at a given location, calculate the vertical displacement based on the dip and horizontal distance between locations.

Answer 1

Correct Answer: 100

Analysis of the map:

The map shows a folded coal seam with topographic contours. The coal seam (shown in black) forms an anticline structure.

Key observations:

1. Location B is marked on the map near the 300m contour
2. The coal seam outcrops at different elevations around the structure
3. At location B, the coal seam appears to be at approximately the 200m contour based on its trace

Determining depth at location B:

From the map:

• Surface elevation at B: approximately 300m (from contour lines)
• Coal seam elevation at B: approximately 200m (where the coal seam trace crosses location B)

Depth calculation:

$$\text{Depth} = \text{Surface elevation} - \text{Coal seam elevation}$$ $$\text{Depth} = 300m - 200m = 100m$$

Answer: 100 m