The zone that acts as a resistance to the flow of ground water from an aquifer to the other aquifer is called as the aquitard. Aquiclude or aquifuge is a wholly impermeable aquitard that permits no ground water from between the aquifers.
In general, while the highly fractured rocks, gravel and sandy materials makes good aquifer, the clay, poorly settled sediments, and non-fractured rocks often forms aquitard.
I believe it was the spread of Christianity although increase trade was amazing. The Chinese did not want the spread of Christianity and was mostly a traditional area.
The Hayward fault is a geologic fault that is capable of massive destruction and is 119 km long fault western base of hills of San Francisco and is parallel to the San Andreas fault. The occurrence of an earthquake of 6.8 magnitudes in 1868 was biggest earthquake in California history.
Recently various geologists have taken time interval of the past five large earthquakes and based on the past earthquakes data the interval of 140 years it will take to the formation of a large earthquake.
