Cape Henlopen Field Trip

We spent the remaining part of my day on a field trip to Cape Henlopen. Cape Henlopen, first settled by the Dutch, was the site of Fort Miles during WWII, when observation towers were built to monitor the coastal waterway and triangulate ship positions for any needed artillery fire. The State began a piecemeal purchasing project from the military until finally acquiring the entire block of land. The park now has bath houses, a fishing pier, and a weave of biking and hiking trails.

GEOLOGICALLY, there are some interesting things going on at Cape Henlopen. Cape Henlopen itself is a migrating spit. As you can see from the map above, there is a tip (spit) pointing out towards open water. The water on the right hand side of the map is coming from the ocean, while on the left and top is Delaware Bay. Waves coming from the ocean primarily run in the direction from the bottom right hand corner to the tip of the spit. Sediment that is picked up in the water through beach erosion is pushed along the shore in a longshore drift fashion, and when it meets the calmer water of the bay the sediment is deposited on the tip of the spit. Over time, the spit has migrated further and further into the bay.

From this image, you can see the suspended sand in the water being carried alongshore.

Now to some photos I took from the field trip. Saw dolphins just off the beach, stratified beach sand, and seined along the fish pier to collect little fishes. Also saw a massive group of horseshoe crabs mating.

Here is one of the Observation towers. It has been reworked to allow people to climb the 128 stairs to the top.

The park is open to campers, and from the top of the observation tower you can see that some have left their mark...the alien is pretty cool (made from a pile of pine needles).

In the distance is another one of the observation towers, as well as a lighthouse

There are still remnants of the military's presence. This is a bunker recessed into a section of the Great Dune. The Great Dune is a geologic feature that has been created due to wind blown sand collecting onshore. The Dune runs parallel to the Delaware Bay, so it is linked to that system. If it were running parallel to the Atlantic, it would be related to the Atlantic.

Here, we are doing a beach profile. One observer sights along a standardized pole towards the horizon. Where the observer sees the horizon intersect the pole in the foreground gives a reading as to the pole's relative height to the observer. In this photo, you can see that the observer is higher than the foreground, so the markings on the pole would read a negative number. Same concept as surveying. Profiles taken of the same area over time can show the dynamically changing beach environment.

Nate's Baywatch moment...

This photo shows Laura sighting towards the horizon past Kendra.

You can see Kendra laying down the pole. We used the height of the pole as the distance between each beach profile reading, so she isn't being lazy, but moving to the next spot for the profile.

Some dolphins decided to join us while we played on the beach

Part of the dune system can be seen in the background.

Here, we are digging a shallow trench in order to see the layering of the beach's sand.

You can see how each layer is distinct in it's thickness as well as grain size. Each time deposition occurs, there are somewhat different conditions, altering the characteristics of the available sediment for deposition. More powerful conditions will coincide with larger grains.

A mud crab...taking a break from burrowing.

For the last activity, we seined for aquatic life. It involves walking with this net in a loop to close around any life in the path of the net.

You can see lots of the little fishes that got caught

A pebble that has been encased with eggs.

Look what Nate found!

Mating Horseshoe crabs.