Deception Pass
Between Whidbey Island and Fidalgo Island there is a narrow strait called Deception Pass. This is the western entrance. To the left is the open water of Rosario Strait and the Strait of Juan de Fuca. To the right is the narrowest part of Deception Pass, where a high steel arch bridge links the two islands. Beyond the narrow strait is Skagit Bay, which is connected to Puget Sound via the long and narrow Saratoga Passage. All around the strait is Deception Pass State Park, where you can find great ocean views, beaches, forests with some surprisingly large trees and odd plants like Indian-pipe. There are something like 18 miles of hiking trails. Nice place.
The geology is also unusual -- it is the boundary between two terranes (a terrane is something like a giant piece of land riding on top of a tectonic plate), which were crushed together in the distant geologic past. The result, especially visible on the north side of the strait, are twisted rocks, cracked, broken, folded and deformed in myriad ways. More than two terranes are involved in the area's geology. The nearby San Juan Islands are made of many terranes of different rock from different parts of the world, stacked on top of each other like a derailed train accident. You can see many kinds of odd rock at Deception Pass, such as a metamorphized basalt called spilite, chert, shale, and graywackes. There is pillow basalt, old lava tuff, and a plutonic rock called plagiogranite. There are slickenline "cat scratch" cracks and lines all over the rocks. As one description puts it, the rocks here have been "sliced and diced", and "here we have the wreckage of an ancient volcanic island that was spread out on the seafloor". One of the formations I liked was the ribbon chert in shale -- dark rock criss-crossed with webs of narrow bands of white rock (remains of marine plankton blooms).
Since the west side of the strait is the open waters of Juan de Fuca -- practically the Pacific Ocean -- and the east side is a rather large inlet of Puget Sound, far to the south through several straits (Admiralty Inlet, Possession Sound, Saratoga Passage, and Skagit Bay), tidal differences can create amazing currents in Deception Pass.
We arrived at the bottom of low tide, and the waters in the strait were placid. After a couple hours, the tide on the beach was noticeably growing stronger and higher, and the tidal currents began to pick up. The current is strong enough to create whitecaps and waves, and looks quite dramatic. The last time we were at Deception Pass, it was during a particularly powerful tidal current. We stood on the bridge and watched in awe as giant upwellings of water churned and frothed, and were torn out to sea by the current. I'd never seen anything like it.
Deception Pass
Between Whidbey Island and Fidalgo Island there is a narrow strait called Deception Pass. This is the western entrance. To the left is the open water of Rosario Strait and the Strait of Juan de Fuca. To the right is the narrowest part of Deception Pass, where a high steel arch bridge links the two islands. Beyond the narrow strait is Skagit Bay, which is connected to Puget Sound via the long and narrow Saratoga Passage. All around the strait is Deception Pass State Park, where you can find great ocean views, beaches, forests with some surprisingly large trees and odd plants like Indian-pipe. There are something like 18 miles of hiking trails. Nice place.
The geology is also unusual -- it is the boundary between two terranes (a terrane is something like a giant piece of land riding on top of a tectonic plate), which were crushed together in the distant geologic past. The result, especially visible on the north side of the strait, are twisted rocks, cracked, broken, folded and deformed in myriad ways. More than two terranes are involved in the area's geology. The nearby San Juan Islands are made of many terranes of different rock from different parts of the world, stacked on top of each other like a derailed train accident. You can see many kinds of odd rock at Deception Pass, such as a metamorphized basalt called spilite, chert, shale, and graywackes. There is pillow basalt, old lava tuff, and a plutonic rock called plagiogranite. There are slickenline "cat scratch" cracks and lines all over the rocks. As one description puts it, the rocks here have been "sliced and diced", and "here we have the wreckage of an ancient volcanic island that was spread out on the seafloor". One of the formations I liked was the ribbon chert in shale -- dark rock criss-crossed with webs of narrow bands of white rock (remains of marine plankton blooms).
Since the west side of the strait is the open waters of Juan de Fuca -- practically the Pacific Ocean -- and the east side is a rather large inlet of Puget Sound, far to the south through several straits (Admiralty Inlet, Possession Sound, Saratoga Passage, and Skagit Bay), tidal differences can create amazing currents in Deception Pass.
We arrived at the bottom of low tide, and the waters in the strait were placid. After a couple hours, the tide on the beach was noticeably growing stronger and higher, and the tidal currents began to pick up. The current is strong enough to create whitecaps and waves, and looks quite dramatic. The last time we were at Deception Pass, it was during a particularly powerful tidal current. We stood on the bridge and watched in awe as giant upwellings of water churned and frothed, and were torn out to sea by the current. I'd never seen anything like it.