Sulphide Lake is located in

North Cascades National Park North Cascades National Park is an American national park in the state of Washington. At more than , it is the largest of the three National Park Service units that comprise the North Cascades National Park Complex. North Cascades National Pa ...

, in the U. S. state of Washington. Sulphide Lake lies in a

cirque A (; from the Latin word ') is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from Scottish Gaelic , meaning a pot or cauldron) and (; ). A cirque may also be a similarly shaped landf ...

on the southeast slopes of

Mount Shuksan Mount Shuksan is a glaciated massif in the North Cascades National Park. Shuksan rises in Whatcom County, Washington immediately to the east of Mount Baker, and south of the Canada–US border. The mountain's name ''Shuksan'' is derived from ...

. Several major cascades drop as much as into Sulphide Lake including

Sulphide Basin Falls Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds lar ...

which is from melt off the

Sulphide Glacier Sulphide Glacier is in North Cascades National Park in the U.S. state of Washington, on the south slopes of Mount Shuksan. Descending from the summit tower of Mount Shuksan, it is connected to Crystal Glacier to the east. Sulphide Glacier desc ...

. After Sulphide Creek drains from Sulphide lake, it then plunges at least over a series of cascades called

Sulphide Creek Falls Sulphide Creek Falls is a tall, moderately large volume waterfall within North Cascades National Park in Washington state. The falls drop from Sulphide Lake (elevation ) on the southeast side of Mount Shuksan down a narrow flume-like canyon to ...

, which is one of the tallest waterfalls in the U.S. The lake is in a basin with near vertical walls and the rock is

phyllite Phyllite ( ) is a type of foliated metamorphic rock created from slate that is further metamorphosed so that very fine grained white mica achieves a preferred orientation.Stephen Marshak ''Essentials of Geology'', 3rd ed. It is primarily compo ...

and

greenschist Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically and 2–10 kilobars (). Greenschists commonly have an abundance of green minerals such as chlorite ...

. Above the lake on the cliffs below

Crystal Glacier Crystal Glacier is in North Cascades National Park in the U.S. state of Washington, on the south slopes of Mount Shuksan. Descending from just east of the summit of Mount Shuksan, near its origination point, Crystal Glacier is connected to the l ...

a 0.3 mile wide band stained red in color (from

iron oxide Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of w ...

) is exposed that runs for about 2.5 miles. This band is rich in the iron sulfides

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue giv ...

and

pyrrhotite Pyrrhotite is an iron sulfide mineral with the formula Fe(1-x)S (x = 0 to 0.2). It is a nonstoichiometric variant of FeS, the mineral known as troilite. Pyrrhotite is also called magnetic pyrite, because the color is similar to pyrite and it ...

.Geology and Mineral Resources of the Northern Part of the North Cascades National Park, Washington.
Geological Survey Bulletin 1359. Presumably this is the source of the lake's name.

References

{{authority control Lakes of Washington (state) North Cascades National Park Lakes of Whatcom County, Washington