Porteau Cove Sill

Porteau Cove Sill

Situated on the most southerly fjord in North America, Porteau Cove Provincial Park features views to the mountains encompased by the Átl’ka7tsem/Howe Sound UNESCO World Biosphere Region. But the best feature of all is the one you can’t see: the submarine Porteau Cove Sill.

The “sill” is actually a 13,000-year-old terminal glacial moraine, a remnant of the final advance of the Squamish Valley Glacier, a lobe of the Pleistocene Cordilleran Ice Sheet that formed Howe Sound; once the ice had fully melted, sea levels rebounded to fill the fjord. If you look around the area, the rocks show abundant signs of glacial scouring and striations.

The moraine itself rises ~300 metres from the sea floor to just 30 metres below the ocean’s surface and provides habitat for unique North Pacific sea life, attracting scuba divers from around the world. An old ship has also been sunk in the park to provide interest for divers.

  • submarine moraine
  • glacial scouring and striations
  • Howe Sound UNESCO World Biosphere Region


A prominent terminal moraine of the last Pleistocene glacial advance some 13,000 years ago, submerged by rising post-glacial sea levels.
Pillars: Glaciation



Porteau Cove Provincial Park lies 43 kilometres north of Vancouver on Hwy 99.


Parking, washrooms.

Protection and guardianship are at the heart of the Geopark philosophy. We ask that you treat the land with the same reverence as its original inhabitants, and not remove anything from a site but what you’ve brought to help preserve it for future generations.


Decimal Degrees (DD)

49.559715, -123.235480

Degrees Decimal Minutes (DDM)

49° 33.5829' N   123° 14.1288' W

Degrees Minutes Seconds (DMS)

49° 33' 34.974" N  123° 14' 7.728" W

What Are Pillars?

The Fire & Ice Aspiring Geopark comprises four main geological pillars referenced in all interpretive material: (M)ountain Building, (G)laciation, (V)olcanism and (C)ollapse.


Mountain building can involve several processes that contribute to the formation of mountains, such as the collision of tectonic plates that result in folding, faulting, metamorphism and the creation of subduction zones associated with volcanic activity and igneous intrusion.


Glaciation refers to landform phenomena associated with the formation, movement and recession of glaciers and ice sheets. In temperate latitudes such as British Columbia, montane glaciation at higher altitudes is the norm while continental glaciation occurred during Ice Ages like the recent Pleistocene.


Volcanism is the eruption of subterranean molten rock (magma) and gasses onto the surface of the planet and includes the production of volcanic landforms and the effects of eruptions and flowing lava on pre-existing surface formations.


Collapse is a term that refers broadly to both slow processes of destabilization and erosion by wind, water and ice, as well as rapid processes like rockfall and landslides.

Whether acting as primary or secondary forces, one or more of these processes figure in the creation of each geosite.