Question

Which of the materials listed has a low permeability and often a high porosity, actually swelling in volume as it absorbs excess water?

A) Gravel
B) Sandstone
C) Clay
D) Limestone

Answer 1

Clay has a low permeability and a high porosity, absorbing water but preventing fluid flow due to the fine, poorly connected particles it contains.

Step-by-step explanation:

The material which has a low permeability and can often have a high porosity, swelling in volume as it absorbs excess water is C) Clay. Clay consists of fine particles of silt that give it plasticity and cohesion when water is added. The interconnected pores allow water to be absorbed and retained by the clay, leading to swelling. Although a geologic material might be porous, which is the case with clay as it can hold a significant volume of water in its void spaces, its fine particles are not well-connected, making it impermeable. This means that while clay can absorb water, it doesn't allow water to flow through it easily, making it unsuitable as an aquifer but effective as a confining layer that prevents water flow.

Answer 2

Clay is a material with low permeability and high porosity that swells as it absorbs water due to its fine particles and plate-like structure limiting water flow.

Step-by-step explanation:

Among the materials listed, clay has a low permeability and often a high porosity, which leads to it swelling in volume as it absorbs excess water. This characteristic is due to the fine grains and the plate-like structure of clay particles, which can hold water but restrict its flow due to the poor interconnection of the pore spaces. Materials like gravel and sandstone, on the other hand, are more permeable and make better aquifers because of their well-interconnected pore spaces.