By locating these tremor signals, the fluid pathway of Old Faithful geyser down to a depth of ~260 feet (80 meters) is illuminated.

Old Faithful, the most famous geyser in Yellowstone National Park, is fed by a complex plumbing system that extends deep into the Earth's crust. Scientific measurements using seismic sensors and temperature probes indicate that the "conduit" or throat of the geyser descends approximately 50 to 100 feet (15 to 30 meters) into the ground, where it connects to a series of cavernous reservoirs. These reservoirs sit above a "hot spot" of magma that is located roughly 3 to 5 miles (5 to 8 kilometers) beneath the surface. The eruption process is a delicate balance of pressure; water from the surface trickles down, is superheated by the magma, and eventually reaches a boiling point where the pressure forces it back up through the narrow conduit. The "depth" of the actual visible vent is relatively shallow, but the thermal energy that powers the 140-foot-high eruptions comes from the vast, molten "Yellowstone Supervolcano" system miles below, making it a surface window into the immense geological power of the North American plate.