Pequaming Tombolo EarthCache

Located in Michigan's upper peninsula's Baraga county. The terrain is generally flat. The roads are asphalted.

Things you will need to log this Earthcache:

1. Camera
2. GPS

To log your find, please E-mail me via my profile, the answers to the following questions:

1. At the posted waypoint walk down to the shore line. While facing towards the open water, tell me which direction the Longshore Drifting is moving the beach sand.
2. While driving from the posted waypoint to the child waypoint, take note of how the terrain looks to your right. Describe to me what the terrain looks like. (Are there elevation changes, type of plant growth).
3. At the child waypoint (Second Stop) walk down to the shore line. While facing towards the open water, tell me which direction the Longshore Drifting is moving the beach sand.

• Not required but always appreciated, post to your online log a photo of your GPS anywhere along the shoreline. Your face can be included if you so wish.

Wave Refraction
Water waves are refracted when their velocity decreases. Water waves slow down as the water becomes shallower. When the wavefront approaches a shoreline, the part of the wave in the shallower water will slow down, causing it to lag behind the part of the wave in the deeper water.

Waves refracting around the island.

Longshore Drifting
The movement of sand and other materials along the shore. Waves usually surge onto a beach at an oblique angle and the push sediments up at an angle. The backwash drains back at a perpendicular angle to the shore, taking sediment with it. Thus there is a zig-zag movement of sediment along the shoreline.

Longshore drifting.

Lee Side
The sheltered or down wind side of an island or other land mass. The side of something that is sheltered from the wind.

Tombolo
A Tombolo is a depositional land form such as a spit or bar which forms an isthmus between an island or offshore rock and a main land shore, two islands or offshore rocks. Tombolos are formed by wave refraction. As waves near an island they are slowed down by the shallow water surrounding it. These waves then refract or bend around the island to the opposite side as they approach. The wave pattern created by this water movement causes a convergence of long-shore drifting on the opposite side of the island. The beach sediments that are moving by lateral transport on the lee side of the island will accumulate there conforming to the shape of the wave pattern. The waves sweep sediment together from both ends of the island. Eventually, enough sediment builds up to form a spit. Which will to grow towards the mainland until it connects, forming a Tombolo. The word comes from the Italian word Tombolo, which is derived from the Latin word tumulus, meaning mound.

Before this Tombolo was formed, there was an island to the northeast that was 1.1 miles offshore. This island was about 2.3 miles long and 0.6 miles wide. The prevailing winds are out of the west and northwest. This means that the northwestern side of the island is hit with the full force of the waves.

Island after the glacier retreated.

When the glaciers melted 10,000 years ago the waves started to pushing sediments against the northwest shoreline of the island. The waves would refract around the ends of the island, pushing sediments around the ends of the island to the middle of southeast or the lee side. Eventually the sediments built up to the point of connecting to the main land.

References used:

• http://www.coastalresearch.nl/glossary/5/view
• http://www.answers.com/topic/tombolo
• http://www.wordiq.com/definition/Tombolo