Hirtle’s Beach - Living or Not EarthCache

Hirtle’s Beach - Living or Not

Hirtle's Beach extends 2.6 km from Point Enrage to the east and Gaff Point to the west. It is a living beach, which changes seasonally with the soft beige sand retreating to Hartling Bay in the winter and returning to provide a lovely crescent sand beach in the summer. The eco-system of the beach has been under a great deal of pressure, in particular, the fragile dune system.

Seasonal Energy Levels

The energy levels of the waves and currents are different in the winter vs. the summer. This affects the beach shape and the amount of sand on the beach. Stronger winter currents leave coarser materials in the winter such as gravel and cobbles.  Much of the sand-sized material is transported offshore. This results in significantly lower sand levels on the beach. While in contrast, the summer has smaller waves and weaker currents and the sand migrates back to the beach. This results in much higher sand levels. So the beach is narrower and rockier in the winter, and wider and sandier in the summer.

Tides

Tidal extremes are greater in the winter than in the summer in the Northern Hemisphere because of the elliptical orbits of the earth around the sun, and the moon around the earth. The moon’s elliptical orbit around the earth is on a 28 day cycle and it is closest to the earth during the “perigee”. The earth’s orbit around the sun is on a 1 year cycle and is closest to the sun during the winter (farther in the summer), this is called the ”perihelion”.

The perihelion is the point in the orbit of a planet, asteroid or comet that is nearest to the sun. It is the opposite of aphelion, which is the point farthest from the sun. The word perihelion stems from the Greek words "peri," meaning near, and "Helios," meaning the Greek god of the sun.

So, we get higher tidal extremes in the winter when we are at perigee and perihelion, because of the increase in gravitational force. This is very significant as only a small increase in a high tide maximum height can be enough to create a situation where waves are breaking directly into the sea cliff. When these high astronomical tides are combined with larger surf generally found in the winter, the potential for coastal erosion is maximized.

Hirtles Beach in October 2010. Not much sand.

Hirtle’s Beach during Summer sands

To log this Earthcache visit the viewing location. Please answer the following questions and send in a timely manner to my geocaching profile or email. Answers not received will result in deleted logs.

Questions:

1. What time of year did you visit (season)?

2. Do you expect sand or rocks, and why?

3. How wide is the sand on the beach from the shoreline?

4. Post a picture in your log with a personal item or hand in picture to prove you were there.

[REQUIRED] In accordance with the updated guidelines from Geocaching Headquarters published in June 2019, photos are now an acceptable logging requirement and WILL BE REQUIRED TO LOG THIS CACHE. Please provide a photo of yourself or a personal item in the picture to prove you visited the site.