Lily Point Marine Park
This park encompasses more than 275 acres with 1.4 miles of saltwater shoreline along Boundary Bay. Forested upland bluffs, beaches, and rich tidelands are just a few unique natural features of this amazing place. Mixed forest of Douglas fir and western red cedar, wildflower meadows, whale watching (summer migration route), various birds and small mammals and thriving tidepools are some of the bonus ecological offerings at this location.
Historically, Lily Point (Chelhtenem) was an important Central Coast Salish reef net fishery and a center of traditional salmon culture. By the late 1800's non-native fisheries dominated the area. Today, only pilings remain of an Alaska Packers Association cannery that once operated here.
Warnings: To visit this earthcache you must take a somewhat steep groomed trail with stairs and switchbacks. Please stick to marked trails. Shortcuts can be very dangerous as the cliffs and bluffs are quite unstable. At the top, stay behind the viewing barriers at all time. That said - this trail and beach are still a wonderful adventure for families and dogs. Just take your time and watch your footing. Bring drinking water, sun protection and even a picnic for the beach!
WHAT IS A COASTAL BLUFF?
A bluff is a type of broad, rounded cliff. A bluff is defined as a steep shoreline slope formed in sediment (loose material such as clay, sand, and gravel) that has three feet or more of vertical elevation just above the high tide line. The key difference between it and a cliff is the material that makes up the slope. Most bluffs border a river, beach, or other coastal area.
Coastal bluffs are formed through a combination of erosion from wind, sea spray, and crashing waves. These bluffs are often more rugged than their inland counterparts, and are more vulnerable to major erosion. The harsh environment of bluffs are also often vital ecosystems. Bluffs provide an ideal nesting spot for fishing birds. Sediment supplied from eroding bluffs is additionally important for sustaining beaches and the nearshore ecosystem.
Bluffs are some of the most common geomorphological features in the world, and lend their names to many cities and neighborhoods.
EROSION
Erosion is the process by which the surface of the Earth gets worn down. Erosion can be caused by natural elements such as wind and glacial ice.
The stability and rate at which a coastal bluff erodes depends primarily on the amount and level of wave action the beach receives, the geology of the bluff (what it's made of), and the characteristics of the adjacent beach. The amount of vegetation covering a coastal bluff and the adjacent shoreline is also directly related to the susceptibility of the bluff face to ongoing erosion. As might be expected, less vegetated bluffs are more likely to be eroding than completely vegetated bluffs.
Another factor that contributes to bluff erosion is the steepness, or slope, of the hillside. The steeper the slope, the more likely it is for a landslide to occur. Weather can also contribute to the erosion process. Strong storms can enhance the size and magnitude of waves battering the shore. Rain can saturate the ground and make it less stable. During winter months, the freeze-thaw cycle of a bluff face can have a similar effect.
Marine-induced bluff erosion is the type most commonly observed, as rising sea levels, tides, and wave action affect the lower slopes. This is a natural process that causes instability, and as the sediment at the base of the bluff erodes away the weight of the mass above it in time causes the hillside to collapse. The occurring landslide then deposits material at the base of the bluff which can act as temporary protection from any further wave damage for a period of time.
Coastal bluffs, especially those in the Puget Sound region of the U.S. state of Washington, are sometimes called feeder bluffs. The constant erosion of feeder bluffs supplies (feeds) sediment to the beaches and seashore downstream below. This active erosion is an important ecological contributor. Notice the sediment deposition both on the upper forest floor and on the beach. Sand eroded off of the bluff face is at times blown up the slope as well as down.
GEOLOGY OF LILY POINT NORTH BLUFF
This area is underlain by glacial marine drift and late glacial outwash. This means that the entirety of Point Roberts was pressed downward by the mass of glacial ice that was over this area 18,000 years ago. The glacial ice was a mile or more thick; it pushed the local earth surface downward many hundreds of feet. As the glacier retreated the sea covered the entire point. At this location there is little exposed glacial marine sediments. More prominently displayed on the bluff is alluvial river sediments, some lake sediments, and possibly some tidal estuary sediments all deposited prior to the last glacial period. The oddity of Point Roberts is that somehow this sequence of alluvial sediments was not eroded away by the glacial ice and stands as an island of elevated alluvial material. (McShane 2012)
The bluff provides a great cross sectional view of an alluvial system. If you look at the layers in the bluffs you can see a couple of pale gray lake units. These pale gray units are not uncommon on Salish Sea bluffs. There is also a layer filled with silt/clay "boulders". Picture a river flowing in a channel lined by river bank silts and clays. As the river under cuts the silt/clay bank blocks of silt/clay collapse into the channel. Some of these remain in the sedimentary layers you see here today. (McShane 2012)
Logging Requirements:
In your log you please mention any other interesting sights on your hike to the site. You may post optional photos from your visit, as well. To claim a find, you must also message me the answers to the following questions that can be answered by reading the cache description and making observations onsite.
- What is the difference between a bluff and a cliff?
- Take an elevation reading at the top viewpoint and then at the beach level. Determine approximately how high the bluffs are from this information.
- Is there evidence of active erosion at these bluffs? Top and bottom?
- How can erosion be beneficial in some cases?
- At the beach viewing WP take and post a picture in your log of yourself (or a personal item or hand) to prove you were there.
References:
https://education.nationalgeographic.org/resource/bluff
Dan McShane, Geologist with permission (https://washingtonlandscape.blogspot.com/2012/04/lilly-point-point-roberts-part-ii-north.html)
The Geologic Map of the Washington Portion of Roche Harbor 1:100,000 Quadrangle (Logan (2003)
Maine Geological Survey: Coastal Bluffs (https://www.maine.gov/dacf/mgs/pubs/mapuse/series/descrip-bluff.htm)
Shipman, Hugh Coastal Bluffs and Sea Cliffs on Puget Sound, Washington (https://fortress.wa.gov/ecy/publications/publications/0406029.pdf )
https://www.whatcomcounty.us/3659/Lily-Point-Marine-Park
This is an earthcache. An EarthCache is a special geological location people can visit to learn about a unique feature of the Earth. EarthCache pages include a set of educational notes along with coordinates. Visitors to EarthCaches can see how our planet has been shaped by geological processes, how we manage its resources and how scientists gather evidence. Typically, to log an EarthCache, you will have to provide answers to questions by observing the geological location. For more information about EarthCaches visit http://www.earthcache.org/.
