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

Step 1: Understanding the diagram.
In the diagram, the coal seam is shown as a horizontal layer, but the beds are dipping. The borehole is located at position B. To find the depth at which the coal seam will be intersected by the borehole, we need to look at the structure of the sedimentary beds between locations M and B. From the diagram, we see that the coal seam is dipping to the east.

Step 2: Calculate the depth.
At location M, the coal seam is at 500m depth. The coal seam is dipping at a rate of 100m per 100m horizontal distance (the beds appear to dip 100m vertically for every 100m horizontally). Therefore, the coal seam at location B will be intersected at a depth of: \[ \text{Depth at B} = 500\,m - 100\,m = 400\,m \] Thus, the coal seam will be intersected at a depth of 400 m.