Which one of the following is a permeable rock that allows water to pass through it?
- A.Granite
- B.Limestone
- C.Quartzite
- D.Sill
Correct answer
Explanation
The correct answer is B, Limestone. Water passes through limestone along its joints and bedding planes, and slowly dissolves the rock as it goes.
Limestone is a sedimentary rock made mainly of calcium carbonate. It is cut by many cracks (joints) and layers (bedding planes), so rainwater soaks into it instead of running off. Rainwater carries dissolved carbon dioxide and is a weak acid, so it widens these cracks, forming sinkholes, caves, stalactites and stalagmites; this is called karst topography. Rocks that let water through like this are called permeable or pervious; such rocks can hold groundwater as aquifers.
A is wrong: granite is a hard, compact igneous rock with interlocking crystals, and it is largely impermeable.
C is wrong: quartzite is a metamorphic rock formed from sandstone whose grains have fused together, so it is dense and does not let water through.
D is wrong: a sill is a sheet-like body of igneous rock that intrudes between rock layers; it is dense and impermeable.
Exam tip: limestone areas = karst — caves, sinkholes and underground streams; granite and quartzite are impermeable.
Practice Questions
View allBroadly both birth and death rates are low in which one of the following stages of demographic transition model?
- A.High stationary stage
- B.Early expanding stage
- C.Late expanding stage
- D.Low stationary stage
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In this last stage both the birth rate and the death rate are low, so the population grows very slowly or stays almost steady.
Read the full explanation →Which one of the following is the deepest, inland and protected port on the east coast of India ?
- A.Chennai
- B.Paradip
- C.Tuticorin
- D.Visakhapatnam
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It is the deepest landlocked and well-protected port on India's east coast. Visakhapatnam port in Andhra Pradesh lies in a natural harbour cut into the land, sheltered by the Dolphin's Nose headland, which protects ships from the waves of the Bay of Bengal.
Read the full explanation →Consider the following characteristics of a type of wind : 1. They occur at upper levels in the atmosphere 2. They are subjected to two forces, a pressure gradient force and the Coriolis force 3. When the forces balance, air moves at right angles to the pressure gradient, parallel to the isobars Identify the type of wind on the basis of the given characteristics :
- A.Jet Stream
- B.Geostrophic Wind
- C.Westerlies
- D.Easterlies
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A geostrophic wind blows high above the surface, where the pressure gradient force and the Coriolis force balance and the air flows parallel to the isobars.
Read the full explanation →Which one of the following major river basins of India is the shortest in length and smallest in terms of catchment area?
- A.Cauvery
- B.Mahi
- C.Penner
- D.Sabarmati
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Of the four, the Sabarmati is both the shortest river and the one with the smallest basin. The Sabarmati rises in the Aravalli hills of Rajasthan and flows about 370 km south-west through Gujarat, past Ahmedabad and Gandhinagar, into the Gulf of Khambhat.
Read the full explanation →Consider the following statements regarding the rotation of the Earth : 1. Since the Earth rotates by 15° each hour, time zones normally differ by one hour 2. At the International Date Line, the calendar day changes - advancing a day for eastward travel, dropping back a day for westward travel 3. Daylight saving time advances the clock by one hour 4. The Moon rotates and revolves about the Earth in the same direction that the Earth revolves around the Sun Which of the statements given above is/are correct ?
- A.1 only
- B.3 and 4 only
- C.1, 3 and 4
- D.2, 3 and 4
Show answer
Only statement 2 is wrong, because it reverses the date-line rule. The Earth turns 360° in 24 hours, or 15° every hour, so neighbouring standard time zones are usually one hour apart (statement 1).
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