The Chuckanut Mountains (from "Chuckanut", a native word for "Long beach far from a narrow entrance"), or Chuckanuts, are located on the northern Washington state coast of Puget Sound

Puget Sound

Puget Sound is a sound in the U.S. state of Washington. It is a complex estuarine system of interconnected marine waterways and basins, with one major and one minor connection to the Strait of Juan de Fuca and the Pacific Ocean — Admiralty Inlet being the major connection and...

, just south of Bellingham, Washington

Bellingham, Washington

Bellingham is the largest city in, and the county seat of, Whatcom County in the U.S. state of Washington. It is the twelfth-largest city in the state. Situated on Bellingham Bay, Bellingham is protected by Lummi Island, Portage Island, and the Lummi Peninsula, and opens onto the Strait of Georgia...

. Being a part of the Cascade Range

Cascade Range

The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...

, they are the only place where the Cascades come west down to meet the sea. The Chuckanuts are considered to be a part of the Puget Lowland Forest Ecoregion.

The range contains Larrabee State Park

Larrabee State Park

Larrabee State Park is a state park in Washington, located six miles south of the city of Bellingham. It was the first state park to be created in Washington.- History :...

, the first State Park to be designated in Washington (1923). Its mountains include:

• Anderson Mountain
• Blanchard Mountain
• Chuckanut Mountain (including North Chuckanut Mountain, South Chuckanut Mountain, and Chuckanut Ridge)
• Galbraith Mountain (also known as North Lookout Mountain)
• King Mountain
• Lookout Mountain
• Sehome Hill
  Sehome Hill Arboretum
  The Sehome Hill Arboretum is an 180 acre park of second growth forest located in the city of Bellingham, Washington, USA, adjacent to the campus of Western Washington University...
  
  
• Squalicum Mountain
• Stewart Mountain
• Toad Mountain

Geology

The Chuckanut Mountains were formed by the folding of the Chuckanut Formation

Chuckanut Formation

The Chuckanut Formation in northwestern Washington , its extension in southwestern British Columbia , and various related formations in central Washington are fluvial sedimentary formations of Eocene age, deposited from about 54 Ma The Chuckanut Formation in northwestern Washington (named after...

 (which is predominantly made up of layers of 55 million year old sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

, conglomerate, shale

Shale

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...

, and bituminous and sub-bituminous coal) and the later Huntingdon Formation (predominantly shale and sandstone) on top, as well as an exposed section of pre-Jurassic-age phyllite

Phyllite

Phyllite is a type of foliated metamorphic rock primarily composed of quartz, sericite mica, and chlorite; the rock represents a gradation in the degree of metamorphism between slate and mica schist. Minute crystals of graphite, sericite, or chlorite impart a silky, sometimes golden sheen to the...

 The Chuckanuts are well-known for their Tertiary Period leaf fossils.

In 1988, an outcrop of metamorphic

Metamorphic rock

Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...

 phyllite, green chert

Chert

Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...

, and milk quartz on Blanchard Mountain was exposed by a construction crew. The outcrop is unique for its unusually large chunks of stilpnomelane

Stilpnomelane

Stilpnomelane is a phyllosilicate mineral of the mica group. It has the formula K81227.Stilpnomelane occurs associated with banded iron formations. It is a metamorphic mineral associated with the blueschist and greenschist facies....

.