V'S RULE

 

• If bed dip upstream:

  • V point upstream

  • Dip of the bed is gentler than contours

  

• For Horizontal beds :

  • V point upstream

• Dip of the bed is same as contours

  

• Bed dip gently downstream:

• V point upstream

• Dip of the bed is sharper or little steeper than contours

  

• Bed dip with stream gradient:

• No v shape

  

• Bed dip steeply downstream:

• V point downstream (only case)

  

• Bed is vertical

• No v shape

  

QUESTIONS

1) A plunging fold will NOT show a V-shaped outcrop pattern on a planar ground surface if the plunge of the fold axis is (JAM-2024)

(A) equal to the dip of the ground surface in the same direction 

(B) steeper than the dip of the ground surface in the same direction 

(C) equal to the dip of the ground surface in the opposite direction 

(D) steeper than the dip of the ground surface in the opposite direction

Solution: 

       There are two conditions when we can't get any V-shape

• If the beds are vertical
• If the beds dip with stream gradient i.e dip of the bed is equal to the plunge of the fold axes and they are in same direction

2) In an undulating topography, a set of uniformly inclined beds show 'V' - shaped outcrop pattern with pointed downstream in a valley. This indicates

(A) Dip of the bed is more than slope of the valley

(B) The dip of the bed is less than slope of the valley

(C) The beds are vertical

(D) The beds are horizontal

Solution : 

        The V- will point downstream only in one case

• If the beds dip steeper than the contours or slope of the valley

3) The given outcrop pattern of a bed (shaded in gray) with respect to contours (dashed lines) indicates that the bed (GATE-2021)

(A) dips upstream.

(B) is horizontal.

(C) dips steeply downstream.

(D) dips downstream at an angle equal to the valley gradient.

Solution : 

• Here dip of bed is gentler than contours
• both are dipping in same direction
• It indicates the bed dip upstream

The bed will point upstream in 3 cases :

• If the bed is dipping upstream
• If the bed is horizontal
• If the bed dip gently downstream

4) Outcrop pattern parallel to topographic contour signifies

(A) Horizontal beds

(B) Vertical beds

(C) Inclined beds

(D) Folded beds

Solution : 

For Horizontal beds

• V point upstream
• Dip of the bed parallel to contours i.e Outcrop pattern parallel to topographic contour

5) In a river valley a dipping bed shows a straight linear outcrop across the river on the geological map. The bed is (GSI-2024)

(A) Folded

(B) Vertical

(C) Dipping at an angle less than valley slope in downwind direction

(D) Dipping at angle more than valley slope in upstream direction

Solution:

The straight linear outcrop will be seen

• If the beds are vertical
• No v-shape will be found