As used in this chapter, the term—

(a) “Secretary” means the Secretary of the Interior;

(b) “geothermal lease” means a lease issued under authority of this chapter;

(c) “geothermal resources” means (i) all products of geothermal processes, embracing indigenous steam, hot water and hot brines; (ii) steam and other gases, hot water and hot brines resulting from water, gas, or other fluids artificially introduced into geothermal formations; (iii) heat or other associated energy found in geothermal formations; and (iv) any byproduct derived from them;

(d) “byproduct” means any mineral or minerals (exclusive of oil, hydrocarbon gas, and helium) which are found in solution or in association with geothermal steam and which have a value of less than 75 per centum of the value of the geothermal steam or are not, because of quantity, quality, or technical difficulties in extraction and production, of sufficient value to warrant extraction and production by themselves;

(e) “known geothermal resources area” means an area in which the geology, nearby discoveries, competitive interests, or other indicia would, in the opinion of the Secretary, engender a belief in men who are experienced in the subject matter that the prospects for extraction of geothermal steam or associated geothermal resources are good enough to warrant expenditures of money for that purpose.

(f) “Significant ¹ thermal features within units of the National Park System” shall include, but not be limited to, the following:

(1) Thermal features within units of the National Park System listed in Section ¹ 1026(a)(1) of this title and designated as significant in the Federal Register notice of August 3, 1987 (Vol. 52, No. 148 Fed. Reg. 28790).

(2) Crater Lake National Park.

(3) Thermal features within Big Bend National Park and Lake Mead National Recreation Area proposed as significant in the Federal Register notice of February 13, 1987 (Vol. 52, No. 30 Fed. Reg. 4700).

(4) Thermal features within units of the National Park System added to the significant thermal features list pursuant to section 1026(a)(2) of this title.

(g) “direct use” means utilization of geothermal resources for commercial, residential, agricultural, public facilities, or other energy needs other than the commercial production of electricity; and ²