Drought Conditions Cause Central Valley Homes To Sink Into The Ground

[KamaAina]

4. You are correct.

https://en.wikipedia.org/wiki/Aquifer#Aquifers_versus_aquitards

Aquifers are typically saturated regions of the subsurface that produce an economically feasible quantity of water to a well or spring (e.g., sand and gravel or fractured bedrock often make good aquifer materials).

An aquitard is a zone within the earth that restricts the flow of groundwater from one aquifer to another. A completely impermeable aquitard is called an aquiclude or aquifuge. Aquitards comprise layers of either clay or non-porous rock with low hydraulic conductivity.