Project Overview
Mount Spurr is an active andesitic stratovolcano in the western Cook Inlet volcanic arc, approximately 70 kilometres west of Anchorage. It hosts surface hot springs, active fumaroles, and a well-documented hydrothermal system fed by a long-lived volcanic heat source. Independent exploration by Ormat Nevada Inc. — one of the world’s largest geothermal developers — confirmed the presence of a regional geothermal anomaly through three field seasons of systematic data collection.
Ormat drilled a deep exploratory well in 2011 that did not encounter commercial temperatures. Ignis H2 Energy Inc. and GeoAlaska LLC reviewed Ormat’s own published data and identified a structural siting error: the well was on the wrong side of a controlling fault. The granite reservoir Ormat was looking for is still there — it has never been drilled.
GeoAlaska holds three active State of Alaska geothermal production leases covering 6,376 acres. The first wells on the correct side of the fault are the planned next step.
A Volcano with Credentials
Mount Spurr is not a subtle geological hint. It is an active andesitic stratovolcano with a documented eruptive history — including a 1992 eruption from its active vent, Crater Peak, that deposited ash across Anchorage. The Alaska Volcano Observatory (USGS) monitors the system continuously.
The geological architecture beneath Mount Spurr is well understood. An active magmatic system feeds heat from depth through the volcanic plumbing into a fractured basement of Tertiary granite — formed approximately 62–69 million years ago. This granite is the target reservoir: a high-temperature fractured rock system, analogous to productive geothermal fields in Iceland and Japan.
Above the granite lies a thick sequence of sedimentary material (the West Foreland Conglomerate Formation) that acts as overburden — not reservoir. The key to accessing the granite is getting on the right side of the controlling structure: the Capps Glacier Fault.
The Hot Springs Are Telling You Where to Look
One of the most important features of the Mount Spurr geothermal system does not require a drill — it springs from the ground.
The Crater Peak Hot Springs sit in the northwestern fault block — on the same side of the Capps Glacier Fault that GeoAlaska proposes to drill. Published geochemical analysis (Garchar & Wendlandt, GRC Transactions, 2012) documents surface temperatures of 64°C and chloride concentrations of 622 milligrams per litre — the strongest hydrothermal surface expression at Mount Spurr. Chloride at these concentrations, at this temperature, indicates a deep hydrothermal fluid source at reservoir temperature.
Hot springs don’t lie. The most energetic part of this system surfaces on the northwest side of the fault — exactly where no well has yet been drilled.
What Ormat Found — and What They Missed
Ormat Nevada Inc. invested three field seasons and significant capital in Mount Spurr between 2009 and 2011. Their program was systematic and professionally executed:
- 1,675 line-kilometres of airborne magnetic survey
- 340 gravity measurement stations
- 49 magnetotelluric (MT) stations across 6 cross-section profiles
- One deep exploratory well to 3,988 feet (Spurr West 26-11)
The well encountered coal at 1,323 feet and reached a maximum temperature of only 60°C at nearly 4,000 feet of depth. The targeted granite reservoir was not found. Ormat described the result as “unexpected and confounding.”
GeoAlaska’s analysis of Ormat’s own published MT inversion data shows why: the MT cross-sections explicitly label the Tertiary granite reservoir on the northwest side of the Capps Glacier Fault. The well was drilled southeast of the fault — in the sedimentary overburden that the MT data also shows on that side. The well found exactly what the geophysics predicted would be there; it just wasn’t the target.
The granite reservoir — identifiable in Ormat’s published dataset — remains undrilled.
The Seismicity Agrees
The Alaska Volcano Observatory maintains a continuous earthquake catalog for the Mount Spurr region. GeoAlaska performed a spatial clustering analysis of this seismic data (using the Anselin Local Moran’s I method), asking a simple question: where is the seismicity concentrated?
The answer: a statistically significant high-density seismic cluster sits centered between GeoAlaska’s proposed well locations — TG-1 and TG-2 — along the intersection of the North Bench and Capps Glacier faults in the northwest block.
Active seismicity beneath a geothermal target is a positive indicator. Earthquakes in this context reflect ongoing movement of hydrothermal fluids through fracture networks — precisely the mechanism that creates and maintains commercial permeability in fractured basement geothermal systems.
The independent geophysics, the surface geochemistry, and the seismicity all point to the same place.
Two Wells. One Answer.
GeoAlaska’s proposed exploration program is focused and purposeful: two temperature gradient wells, sited northwest of the Capps Glacier Fault in the Tertiary granite domain.
- TG-1 targets the North Bench Fault zone — a secondary structural feature in the NW granite block expected to provide both thermal gradient data and direct confirmation of granite lithology at depth
- TG-2 targets the Capps Glacier Fault’s northwest hanging wall — in the heart of the seismic High-High cluster zone — to characterize reservoir temperatures and structural permeability
A Plan of Exploration for both wells has been submitted to and approved by the Alaska DNR (May 2026). These wells are the first direct test of the structural thesis.
Alaska’s Second Geothermal Baseload
The strategic logic for Mount Spurr is identical to Mount Augustine: Alaska’s Cook Inlet natural gas supply is declining, LNG imports will soon push power generation costs above $90/MWh, and an 80% Renewable Portfolio Standard is in effect for 2040. Geothermal baseload — firm, dispatchable, no fuel cost — is the structurally correct answer.
Mount Spurr adds a dimension that Augusta cannot: proximity. At approximately 70 kilometres from Anchorage, Spurr sits materially closer to the Southcentral load centre than Augustine (~300 km southwest). The existing Beluga substation on the west side of Cook Inlet provides an established Railbelt interconnection point — a shorter and simpler transmission path.
A developed Spurr field would deliver approximately 70 megawatts of baseload power within the shortest geothermal-to-Anchorage transmission corridor in Alaska.
Working with Cook Inlet Region Inc.
The Mount Spurr permit area and the route between it and the Railbelt crosses land in which Cook Inlet Region Inc. (CIRI) holds rights as an Alaska Native Corporation. GeoAlaska recognises that a project of this scale, in this location, requires a genuine and mutually beneficial relationship with CIRI and the communities it represents.
CIRI has engaged with Cook Inlet resource development previously, and GeoAlaska’s engagement strategy is built on the understanding that access, transmission, and economic opportunity for the region must be developed together, not extracted unilaterally. This relationship is a project prerequisite — and a reflection of what responsible energy development in Alaska looks like.
Technical Background
The Mount Spurr technical thesis is grounded in publicly available data — primarily Ormat Nevada Inc.’s 2009–2011 exploration dataset, filed with and accessible through the Alaska DNR. GeoAlaska’s structural reinterpretation of this dataset has been developed by the same geoscience team responsible for the Mount Augustine exploration program.
The historical scientific literature on Mount Spurr geothermal potential includes:
- Garchar & Wendlandt (2012), GRC Transactions Vol. 36 — geochemical investigation of Crater Peak hydrothermal system
- Martini et al. (2011), GRC Transactions Vol. 35 — Ormat’s formal resource definition paper
- Turner & Wescott (1986), University of Alaska Geophysical Institute Report R-308 — foundational geothermal reconnaissance
