What is the geologic history of clay?
Clay minerals most commonly form by prolonged chemical weathering of silicate-bearing rocks. They can also form locally from hydrothermal activity. Chemical weathering takes place largely by acid hydrolysis due to low concentrations of carbonic acid, dissolved in rainwater or released by plant roots.
How long does it take for aquifers to form?
The time it takes for surface infiltration to reach an aquifer as deep as 400 feet may take hours, days, or even years, depending on the rate of recharge. In some of the flood-irrigated areas, groundwater levels in nearby domestic wells rise within a few hours to days of flood-up.
What makes a good aquifer?
Aquifers must be both permeable and porous and include such rock types as sandstone, conglomerate, fractured limestone and unconsolidated sand and gravel. Fractured volcanic rocks such as columnar basalts also make good aquifers. However, if these rocks are highly fractured, they make good aquifers.
Why is permeability important for the presence of groundwater?
Permeability is the most important variable in groundwater. Permeability describes how easily water can flow through the rock or unconsolidated sediment and how easy it will be to extract the water for our purposes.
When was clay formed?
Erosion is one source of particles for clay soils and it occurs when water rushes over the surface of rock. However, the largest source of clay particles is from weathering of rocks and soil. During weathering, both physical and chemical changes take place that create the small particles required to form clay soil.
How does clay Formation affect a rock?
glaciers can drag rocks over bedrock , wind carrying sand can wear down rock , and rocks can be worn away in rivers. how does clay formation affect a rock? some minerals transform into clay, the clay absorbs the water expands and causes the rock to crumble. what is needed for a rock to rust?
How were aquifers formed?
An aquifer is a body of porous rock or sediment saturated with groundwater. Groundwater enters an aquifer as precipitation seeps through the soil. It can move through the aquifer and resurface through springs and wells.
How are aquifers formed?
When a water-bearing rock readily transmits water to wells and springs, it is called an aquifer. Wells can be drilled into the aquifers and water can be pumped out. Precipitation eventually adds water (recharge) into the porous rock of the aquifer.
What caused aquifers to form?
Similar to a below-ground sponge, aquifers are the natural accumulation of runoff and precipitation. Below the surface, this runoff then percolates into crevices between rocks, silt and other material.
When did aquifers occur?
The oldest groundwater ever found was discovered 2 miles (2.4 km) deep in a Canadian mine and trapped there between 1.5 and 2.64 billion years ago.
When groundwater reaches an impermeable layer of rock?
To reach an aquifer, surface water infiltrates downward into the ground through tiny spaces or pores in the rock. The water travels down through the permeable rock until it reaches a layer that does not have pores; this rock is impermeable (figure 1). This impermeable rock layer forms the base of the aquifer.
What happens to water that soaks into the ground?
When water from the earth’s soil, plants, and water bodies turns into water vapor, the process is called evaporation. The rest of it soaks or percolates into the soil, called recharge. The water then moves down through the soil as groundwater and is stored in the aquifer below.
What makes the term ‘unconfined aquifer’ false?
The only thing that makes it false is referring to “confined aquifer,” instead of an “unconfined aquifer.” A confined aquifer is an aquifer with layers of generally impermeable rock above and below the aquifer (aquifers tend to run in horizontal layers below ground).
How does subsidence occur in a confined aquifer?
In a confined aquifer if you drill a well, the pressure will push water up the well casing; sometimes all the way to the land surface—no pump is needed! (2) Land subsidence occurs in areas underlain by highly fractured granite, which is readily dissolved by moving groundwater, especially when the water is slightly acidic. This is false.
What are small pockets of water that exist below the water table?
Pockets of water existing below the water table are called aquifer s. An area’s water table can fluctuate as water seep s downward from the surface. It filters through soil, sediment, and rock s.
Do freshwater aquifers exist under the ocean?
Since aquifers exist in generally horizontal layers below the land surface, that means freshwater aquifers can extend underneath the oceans. Drilling a well near the coast can still tap a freshwater aquifer. Saline aquifers also exist both underneath the oceans and under the land surface.