Puget Sound and Coastal Geology | WA (2022)

Puget Sound and Coastal Geology

Puget Sound and Coastal Geology | WA (1)

Cape Flattery, Makah Reservation. Photo credit: Jessica Czajkowski, WGS.

Puget Sound and Coastal Geology | WA (2)

Point of Arches, Shi Shi Beach. Photo credit: Liz Thompson.

Puget Sound and Coastal Geology | WA (3)

(Video) Geology of Seattle and the Puget Sound

Giant's Graveyard, Third Beach. Photo credit: Liz Thompson.

Puget Sound and Coastal Geology | WA (4)

Puget Sound from Pikes Place Market, Seattle. Photo credit: Dave Norman, WGS.

Puget Sound and Coastal Geology | WA (5)

Lummi Island and Mount Baker. Photo credit: Tim Walsh, WGS.

Puget Sound and Coastal Geology | WA (6)

Tacoma Narrows Bridge. Photo credit: Dave Norman, WGS.

The geology of Washington’s coast and Puget Sound is complex and beautiful. These attributes make Washington a great place to live, work and play. While many derive their livelihoods directly from these resources, we all depend on healthy coast and Puget Sound ecosystems, either directly or indirectly and whether we are aware of it or not.

(Video) Top 5 Puget Sound Washington Crabbing Locations

The majority of the state's population lives and works in the Puget Sound or other coastal areas. Because of this, the Washington Geological Survey has worked hard for over 125 years to provide the best-available science for planning and decision-making associated with the geologic hazards of these areas. We continue this legacy today, and the vast majority of our work is aimed at improving our understanding of geologic hazards.

Geologic Hazards

The most common hazards in the Puget Sound area and along marine coastlines of Washington include:

Clicking on these tiles will take you to a page where you can learn more about the specific hazard. Other hazards include Volcanoes and Lahars and Hazardous Minerals.

We publish a large variety of hazard maps. These can be found on our Geologic Hazard Maps page or in the Maps section of our Publications and Maps page. You can also find these data on the Geologic Information Portal.

What We Do

Survey geologists work extensively in the Puget Sound and coastal areas— including Washington’s outer coast and the Strait of Juan de Fuca—to increase our geologic understanding of these populated areas. We are proud to continue the legacy of pioneering geologic study that began around the turn of the 20th century when J. Harlen Bretz published a history of Puget Sound glaciation in 1913.

Geology – We have mapped thousands of square miles of geology in the Puget Lowland to provide a basic understanding of the geology underfoot. This critical information is used by planners, emergency managers, and developers as a basis for understanding the geologic risk of an area.
Active faults – We find and characterize faults throughout the region to learn which faults are active and how much risk they pose to society. Because the Puget Lowland is covered with thick forests and vegetation, finding faults can be difficult. Survey geologists increasingly use lidar in order to "see through" the trees to the ground surface. This new technology increases the visibility of active faults, but lidar coverage is not yet continuous everywhere.
Tsunamis – Tsunamis are a significant threat to the coastal areas of our state. We work with national and regional agencies to model and publish tsunami inundation maps. We then develop and publish tsunami evacuation brochures for areas of high risk. These evacuation brochures are available in published (paper) form, as an interactive online map, and as downloadable PDFs.
Landslides – We work with other state and local agencies to catalog existing mapped landslides through the Puget Sound region. To supplement this work we are developing a comprehensive and detailed landslide inventory based on the best-available lidar data. Lidar provides a huge advantage for mapping landslides. Landslides and landslide deposits that were masked by thick vegetation are often clearly revealed with lidar.
Seismic Hazards – We have developed and published a series of maps and reports about ground response to seismic shaking (earthquakes). These maps include: NEHRP site class maps, liqeufaction susceptibility maps, and seismic design category maps. We also offer a suite of datasets that show the predicted damage for several earthquake scenarios. You can find these seismic scenarios here. All these data are used by local, county, regional, and state planners and emergency managers. The products are also designed to help the public understand their risk from these hazards.
Lahars and Volcanic Hazards – We work with national and regional agencies to develop and publish maps of volcanic hazards. We have completed these maps for the area around Mount Rainier (including low-lying areas all the way to Seattle/Tacoma). Remaining areas near other volcanoes will become available as they are completed.
Multi-Hazard Analysis – We are developing a state-wide county by county assessment of all hazards. These data will become available as they are completed.
Subsurface Data – We collect and maintain a database of all publicly available subsurface information for Washington. These data include water wells, geotechnical boreholes, gravity and magnetic data, oil and gas wells, geothermal wells, and a depth to bedrock 3D model for the Puget Lowland.
Earthquakes and Faults – We maintain a database of all active faults and re-located earthquakes in Washington. These data help scientists and planners identify potential seismic hazards throughout the state.
Shallow Landslide Hazard Forecast Map – In cooperation with NOAA, we have developed a model based on recent and predicted rainfall data that may forecast hazards and may reduce losses from landslides.

Puget Sound Geology

The Puget Sound is part of the larger geologic province of the Puget Lowland. Both were sculpted by the thick and extensive glaciers that advanced south to just beyond Olympia. Glacial till (sediment deposited directly by the ice) and outwash (sediment deposited by meltwater in front of the glacier) make up most of what is found at or near the surface. These glacial sediments were deposited during the last 2 million years by numerous glacial advances, the most recent of which was around 15,000 years ago.

(Video) Fly Fishing South Puget Sound Beaches for Coastal Cutthroat & Resident Coho Salmon

The glacier covered the area in several thousand feet of ice. As glaciers move, sediment is scraped off the ground and transported on top of, within, beneath, and in front of the ice. This created many of the long and narrow hills and lakes we see today. Glaciers are capable of lifting, mixing, and moving rocks from the size of very large boulders to clay. The meltwater streams that flow in front of advancing and retreating glacial front can also move significant amounts of sediment.

Though glacial sediment covers a great deal of the Puget Lowland, isolated exposures of bedrock are found throughout. The southern area of the Puget Lowland is partly covered with ancient lava flows, similar to those found at Mount Rainier and Mount St. Helens. To the north, the San Juan islands are composed of metamorphic rocks accreted onto North America 160 million years ago.

For a longer explanation of Puget Sound’s geology, see the Puget Lowland geologic province page:

Washington Coast Geology

Unconformity on Fourth Beach between dipping sediments below and flat sediments above. Photo credit: D. Norman.

The Pacific coast of Washington is characterized by river and alpine glacier sediments above basalt and marine sedimentary rocks that were accreted to the continent.

The southern coastline lined with sandy sediment that works its way from the mouths of the rivers. This sediment forms beaches and sand spits like Long Beach, Ocean Shores, and Westport. Sediment from the Columbia River migrated north on ocean tides and formed the Long Beach peninsula, which is still actively growing.

The northern coast is made up of basalt from lava flows on the ocean floor that have been accreted onto the continent over the last several million years. For more information on how this works, see the Olympic Mountains page.

(Video) Puget Sound’s Exotic Terranes | Nick on the Rocks

Extensive work has been done by Survey geologists to characterize the geology of coastal regions. Particularly, the work of Weldon Rau has provided a comprehensive overview of the geology of Washington's outer coast. See the Resources section below to download his publications.

Resources and More Information

Foraminifera, Stratigraphy, and Paleoecology of the Quinault Formation, Point Grenville-Raft River Coastal Area, Washington
Geology of the Washington Coast Between Point Grenville and the Hoh River
Washington Coastal Geology Between the Hoh and the Quillayute Rivers
Glaciation of the Puget Sound Region
The Puget Lowland earthquakes of 1949 and 1965—Reproductions of Selected Articles Describing Damage (1986)
Thickness of Unconsolidated Sediments, Puget Lowlands, Washington (1974)
Models of Bedrock Elevation and Unconsolidated Sediment Thickness in the Puget Lowland (2014)
Geologic Information Portal
(Video) Geological History of Puget Sound

FAQs

How was Puget Sound formed? ›

A low area, called a trough, formed between the mountains. Over time, water filled in the trenches and formed Puget Sound. This all took place during the beginning of the Pleistocene Epoch which is also often called the Ice Age. During this period, glaciers covered the Puget Sound region at least seven different times.

What kind of rocks are in the Puget Sound? ›

The Pacific coast of Washington is characterized by river and alpine glacier sediments above basalt and marine sedimentary rocks that were accreted to the continent.

What is unique about Puget Sound? ›

Its 2,500-mile shoreline extends from the northern Deception Path to the southernmost Olympia, making it the second-largest estuary in the U.S. just after the Chesapeake Bay. It's also a considerably deep body of water. The deepest point, between Whidbey Island and Tacoma, is 600 feet.

What is the geology of Seattle? ›

Seattle lies within the Puget Sound Lowland, an elongate structural and topographic basin bordered by the Cascade and Olympic Mountains. The geology of the Seattle area is dominated by a complex, alternating, and incomplete sequence of glacial and interglacial deposits that rest upon an irregular bedrock surface.

How was Washington's geology formed? ›

The terranes of Washington resulted from continental evolution whereby pieces of ancient continents have broken off and reattached to form different continents. The oldest rocks in Washington can be traced back to the supercontinent of Rodinia, which is thought to have formed 1.1 billion years ago.

Is the Puget Sound considered the ocean? ›

Puget Sound (/ˈpjuːdʒɪt/) is a sound of the Pacific Northwest, an inlet of the Pacific Ocean, and part of the Salish Sea. It is located along the northwestern coast of the U.S. state of Washington.
...
Puget Sound
Native nameWhulge (Lushootseed)
EtymologyPeter Puget
Part ofSalish Sea
17 more rows

Can diamonds be found in Washington State? ›

When it comes to diamonds, there is no exact location to find them; however, they occur randomly in association with volcanic rock. You might discover diamonds in such areas in Washington.

Are beach rocks worth money? ›

These rocks break down with time into tiny pieces known as stones or pebbles.
...
The Top 10 Valuable Beach Stones in the World Today.
No.Beach StonesPrices (per carat/piece)
6.Serpentinite$10-$20 per piece
7.Petrified wood stone$0.25-$10per pound
8.Jasper$2- $5per carat
9.Calcite$1-$5 per piece
6 more rows

Can you take rocks from Washington beaches? ›

The ocean beaches are famous for their agates, jaspers, and other quartz minerals, while the banks of the rivers and creeks are often panned for gold.
...
Seattle & Northwest Washington Rockhounding Locations.
LocationRocks & Minerals
Sol Duc River, in gravelsAgate, Chert, Jasper
Ozette River, in gravelsGold (placer)
17 more rows

What is the geography of Puget Sound? ›

It is a complex estuarinesystem of interconnected marine waterways and basins connected to the Pacific Ocean through the Strait of Juan de Fuca. Puget Sound extends approximately 100 miles from the north where it meets the Strait of Juan de Fuca at Admiralty Inlet to Olympia, Washington in the south.

Why do they call it Puget Sound? ›

The sound, called Whulge by the Salish Indians, was explored in 1792 by British navigator George Vancouver and named by him for Peter Puget, a second lieutenant in his expedition, who probed the main channel.

What is important about Puget Sound? ›

Puget Sound is critical to our environment, culture, and economy. About two-thirds of the state's population lives in the Puget Sound region. Our nation's second largest marine estuary faces a number of challenges related to population growth and development, as well as habitat loss and multiple sources of pollution.

Can Puget Sound have a tsunami? ›

Tsunamis can be generated in Puget Sound by both landslides and earthquakes. The most frequent cause of Puget Sound tsunamis is landslides. The 1949 Olympia earthquake triggered a landslide in the Tacoma Narrows that caused a 6 to 8-foot tsunami that affected nearby shorelines three days after the earthquake.

How far down is bedrock in Seattle? ›

Depth to bedrock in the northern part of the city ranges from two to four thousand feet (Hall and Othberg, 1974). Sediments of earlier Quaternary and Pliocene age are probably present at depth, but such materials are not exposed in the city.

Why are Washington beaches so rocky? ›

Overlying the bedrock all along this coast are deposits of sand and gravel that were laid down by streams from glaciers during the Pleistocene Epoch some 17 to 70 thousand years ago. The picturesque rock formations so prominent along the Washington Coast have undoubtedly aroused the curiosity of many people.

Where are the oldest rocks in Washington state? ›

The oldest rocks of Washington State can be found in the Northeastern Highlands, which contain the Northern Rocky Mountains as well as the Kootenay Arc and the Okanogan Highlands (Figure 2.10). The Northern Rocky Mountains defined the ancient edge of the North American continent during the Precambrian.

How old are the rocks in Washington state? ›

According to the available data, the oldest rock formations exposed along this part of the Washington coast date back no more than 50 million years. This is relatively young when compared to an age of 4.5 billion years usually calculated for the older rocks of the earth's crust in other areas of the world (fig.

Are there any sharks in the Puget Sound? ›

The Sixgill Shark is found all over the world including Puget Sound. They have been observed as deep as 6,000 feet but are commonly found around 300 feet. They are a rare sight in Puget Sound, so if you're diving and you see one, don't feel scared ... feel lucky!

What is at the bottom of Puget Sound? ›

The bottom of the Sound is made up of a series of valleys and ridges, or sills, which disrupt the movement of water and help it mix. Two of the most important sills are at Admiralty Inlet and the Tacoma Narrows. The second largest estuary in the United States, Puget Sound has 3,790 kilometers of shoreline.

What is the deepest spot in Puget Sound? ›

The deepest part of Puget Sound is off Point Jefferson, five miles northwest of Seattle, where the sea floor drops to 930 feet. Rockfish, on average, are found at depths of around 900 feet—but they've been documented well past 3,500 feet and are adapted for extreme high-pressure, low oxygen environments.

Do you need a permit to pan for gold in Washington state? ›

A formal HPA is not required for recreational panning and prospecting if you use a gold pan, mini-rocker box, or non- motorized, small sluice box. You must have a formal HPA for sluicing and dredging.

Where can I find gold nuggets in Washington state? ›

The most interesting gold occurrence in Washington is on the east side of the Cascades near the town of Liberty in Kittitas County. In an area known as the Liberty Mining District or Swauk Mining District, the richest gold placers in Washington are found.

Can you find opals in Washington state? ›

Washington has an extraordinary variety of rocks and fossils. Collectors have the opportunity to find beautiful agates, amethysts, garnets, jaspers, opals, and even the occasional nugget of gold. Our state also has a plethora of fossils including crinoids, clams, trilobites, snails, corals, and at least one dinosaur.

What kind of stone are never found in the ocean? ›

What kind of stone is never found in the ocean? Sent by: Age: A stone that is dry.

How do you tell if a rock has gold in it? ›

One of the easiest and most telling tests for gold that you can perform on your rock is for hardness. This test is an application of Mohs hardness scale, which compares the hardness of different minerals by scratching them against one another.

Can you find rose quartz on the beach? ›

Quartz is the main component in the sand on many beaches across the world. In the same way, sand particles are brought to shore, bigger pieces of quartz can be brought in by the tide as well. Quartz can be found on the beach.

How do you tell if a rock is an agate? ›

A Beginners Guide to Agate Identification - YouTube

Is there jade in Washington State? ›

Washington is one of the very few locations in the world where botryoidal jade is found. We call them Dragon Bubbles. But the best stones often find their way out of the state and lose their identity in the inscrutable realm of the international jade collector.

Is the Puget Sound a fjord? ›

Puget Sound is a deep fjord estuary that lies within the broader Salish Sea. As a saltwater body, it is far from being uniform: each basin, carved by retreating glaciers more than 10,000 years ago, varies in its physical, chemical, and biological properties. Together, the basins contain an astounding diversity of life.

Which natural resources are found in the Puget Sound region? ›

The economy of the region is largely tied to the sound and its natural resources, such as lumber, shellfish, and recreation.

Is the Puget Sound a river? ›

Puget Sound is a large inland estuary connected to the Pacific Ocean. It is about 95 miles long and 1 to 5 miles wide with it's northern boundary at Admiralty Inlet and ending in the south at the city of Olympia.

Is the Puget Sound less salty than the ocean? ›

This is also apparent in the salinity of the Sound, which averages about 28.5 parts per thousand, compared to about 34 for the nearby Pacific. This means that the Sound is roughly 83% seawater. Even as far south as Budd Inlet near Olympia it is still two-thirds seawater.

Can you swim in the Puget Sound? ›

A large number of beaches in the Puget Sound region have high levels of fecal bacteria causing the water to be unsafe for swimming and water contact. Local health departments have issued no-contact advisories for 10 beaches in four counties.

Is Puget Sound fresh or saltwater? ›

All estuaries, including Puget Sound, are par- tially closed-off waterbodies where freshwater from rivers and streams mixes with salt water from the ocean.

What does Puget mean? ›

[ n ] a nose curved downward like the beak of a hawk.

What does sound mean in Puget Sound? ›

In areas explored by the British, the term "sound" was applied to inlets containing large islands, such as Puget Sound. It was also applied to bodies of open water not fully open to the ocean, or broadenings or mergings at the openings of inlets.

How deep is the Puget Sound under the Narrows Bridge? ›

The water is over 200 feet deep. Swift, treacherous tides moving at over 8.5 miles per hour (12.5 feet per second) sweep through the channel four times a day.

Will the San Andreas fault affect Washington? ›

Yes. It's not a matter of if, but when. The Pacific Northwest is commonly known to be the most dangerous earthquake hotspot outside of California. So while the San Andreas Fault Line is a well known danger to Californians, Pacific Northwesterners also need to be prepared!

How far inland will the Cascadia earthquake reach? ›

about 70-100 miles The Cascadia Subduction Zone is a 600-mile fault that runs from northern California up to British Columbia and is about 70-100 miles off the Pacific coast shoreline.

How far would a tsunami reach in Seattle? ›

Waves could last more than 3 hours and the department said that they could be as high as 42 feet at the iconic Seattle Great Wheel. Waves could overtake Lumen Field, the home of the Seattle Seahawks, and in some areas of impact, waves could travel up to three miles inland.

Is Seattle on the fault line? ›

The Seattle Fault runs east-west just south of downtown, yet we did not know our city straddled an active fault until the 1990s.

What kind of rock is in Seattle? ›

Seattle's geologic record begins with Eocene deposition of fluvial arkosic sandstone and associated volcanic rocks of the Puget Group, perhaps during a time of regional strike-slip faulting, followed by late Eocene and Oligocene marine deposition of the Blakeley Formation in the Cascadia forearc.

Is Seattle in a seismic zone? ›

Crustal earthquakes are expected on the Seattle Fault Zone, which is the primary but not only source for this type of quake in Seattle. An example of a crustal earthquake is the magnitude (M)6.2 Christchurch, New Zealand earthquake that occurred in 2011.

When did Puget Sound form? ›

The Puget Sound region was formed by the collision and attachment of many terranes ("microcontinents") to the North American Plate between about 50 to 10 million years ago. About 15,000 years ago during the Vashon Glaciation, the Puget Sound region was covered by a lobe of the Cordilleran Ice Sheet.

Why do they call it Puget Sound? ›

The sound, called Whulge by the Salish Indians, was explored in 1792 by British navigator George Vancouver and named by him for Peter Puget, a second lieutenant in his expedition, who probed the main channel.

What is at the bottom of Puget Sound? ›

The bottom of the Sound is made up of a series of valleys and ridges, or sills, which disrupt the movement of water and help it mix. Two of the most important sills are at Admiralty Inlet and the Tacoma Narrows. The second largest estuary in the United States, Puget Sound has 3,790 kilometers of shoreline.

What does sound mean in Puget Sound? ›

In areas explored by the British, the term "sound" was applied to inlets containing large islands, such as Puget Sound. It was also applied to bodies of open water not fully open to the ocean, or broadenings or mergings at the openings of inlets.

Is the Puget Sound a fjord? ›

Puget Sound is a deep fjord estuary that lies within the broader Salish Sea. As a saltwater body, it is far from being uniform: each basin, carved by retreating glaciers more than 10,000 years ago, varies in its physical, chemical, and biological properties. Together, the basins contain an astounding diversity of life.

When did the glaciers leave Seattle? ›

About 16,900 years ago, the Vashon glacier begins to melt and recede from lands that will come to be known as the Puget Sound region and the Columbia Basin region. By 15,000 years ago, the glacier has retreated to the border of present-day Canada.

Where is the deepest part of Puget Sound? ›

The deepest part of Puget Sound is off Point Jefferson, five miles northwest of Seattle, where the sea floor drops to 930 feet.

Is the Puget Sound less salty than the ocean? ›

This is also apparent in the salinity of the Sound, which averages about 28.5 parts per thousand, compared to about 34 for the nearby Pacific. This means that the Sound is roughly 83% seawater. Even as far south as Budd Inlet near Olympia it is still two-thirds seawater.

Can you swim in the Puget Sound? ›

A large number of beaches in the Puget Sound region have high levels of fecal bacteria causing the water to be unsafe for swimming and water contact. Local health departments have issued no-contact advisories for 10 beaches in four counties.

What is important about Puget Sound? ›

Puget Sound is critical to our environment, culture, and economy. About two-thirds of the state's population lives in the Puget Sound region. Our nation's second largest marine estuary faces a number of challenges related to population growth and development, as well as habitat loss and multiple sources of pollution.

Are there great whites in Puget Sound? ›

Great White

They grow up to 16 feet long (with the largest great white reaching more than 20 feet), and eat seals, dolphins, bony fish, and porpoises. Additionally, they're not found in the Puget Sound, but they do occasionally approach the coastal waters of western Washington.

Are there any sharks in Puget Sound? ›

The Sixgill Shark is found all over the world including Puget Sound. They have been observed as deep as 6,000 feet but are commonly found around 300 feet. They are a rare sight in Puget Sound, so if you're diving and you see one, don't feel scared ... feel lucky!

Why is Lake Washington so deep? ›

Prior to construction of the canal, the only significant inflow was from the Sammamish River in the north. Construction of the canal resulted in the lowering of the lake 9 feet to its present level, leaving the Black River dry and the Cedar River diverted into Lake Washington.

What is difference between a sound and a bay? ›

A sound is an inlet of the ocean substantially larger than a bay, and it may be less protected. Sounds are often characterized by large open spaces of water. A sound can be deeper than a bay, and is certainly deeper than a bight, a name for a shallow ocean inlet.

What is the sound of a waterfall called? ›

The sound made by waterfalls is called a burble.

What is the difference between the sound and the ocean? ›

While the ocean is tidal, the sounds' calm waters are dependent on wind conditions. You will consistently find much calmer water in the sound making these areas great for sitting in your beach chair and spending a relaxing day with your family.

Videos

1. The Puget Sound Rocks!
(Puget Sound Estuarium)
2. Beautiful Washington. Episode 1 - Scenic Nature Documentary Film about Washington State
(4K Relaxation Channel)
3. The Best of Puget Sound Diving
(Aaronatevergreen)
4. Marine Life Identification, Puget Sound, WA 🐟 🐠
(Cooper's Amputee Lifestyle)
5. Seattle's Waterway to the World
(Vaun Raymond)
6. Kayak Fishing Washington Coastal Waters For Ugly (& delicious) Fish
(Gig Harbor Fly Shop)

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