Normal Fault

Normal Fault

High angle fault that results from extensional stress and forms a steeply dipping planar structure. Slip movement during an earthquake is vertical and down dip. The down-dropped block is called the hanging wall and the uplifted block is called the footwall.

Geothermal Glossary

Word of the Week – Proppant

Word of the Week – Proppant

Proppant Sand-sized solid grains that are injected in a fluid suspension and used to hold open stimulated fractures in a geothermal reservoir.

Word of the Week – Propylitic Alteration

Word of the Week – Propylitic Alteration

Propylitic Alteration A term borrowed from studies of hydrothermal ore deposits that refers to an assemblage of secondary hydrothermal minerals which forms in igneous rocks. This assemblage is made up of chlorite, illite, feldspar (both Na and K-rich varieties),...

Word of the Week – Rhyolite

Word of the Week – Rhyolite

Rhyolite Light colored fined grained volcanic rock composed of glass, quartz, K-feldspar and plagioclase, with relatively high silica (69-77 wt %). The composition reflects partial melting of continental crust. Rhyolitic volcanism is a feature of both Yellowstone...

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