Yankee Harbour on Greenwich Island
This wonderful natural harbor is surrounded by glaciers. It’s an almost perfect safe anchor for ships, which is why it was used by sealers for many years. You enter Yankee Harbour via Shopski Cove, which is between Spit Point and Glacier Bluff on Greenwich Island. You can also look across McFarlane Strait towards Half Moon Island and glaciers and the snow cap across the peaks of Livingstone Island, one the most spectacular islands in the South Shetlands.
The other great attraction here is the large Gentoo penguin colony, with over 4,000 breeding pairs making Yankee Harbor their home. As well as the penguins, skuas often nest here - their feathers camouflaging them against the rocky ground making them very hard to see.
The landing beach here is terraced, and there is a melt-pool from the glacier on the eastern end. Depending on the conditions and breeding status of the penguins, some longer walks in the area are possible along the curved gravel spit.
Geology
Solis Glacier is a glacier on Greenwich Island in the South Shetland Islands, Antarctica extending 2.8 km in southeast-northwest direction and 1.8 km in southwest-northeast direction and draining the north slopes of Breznik Heights to flow northwestwards into Yankee Harbour. Greenwich Island at Yankee Harbour has a large terraced beach area and includes a melt-pool to the east. Beyond the beach there is a steep scree slope that rises to a rugged knife-edge summit.
The glacial moraine at Yankee Harbor was laid down when the glacier on Greenwich Island advanced during the last glaciation. The moraine was likely under water at that time, but was left behind when the glaciers of the South Shetlands retreated. Those glaciers 5 to 6 thousand years ago were likely more than two kilometers thick and had depressed the earth’s crust. Following retreat and thinning, the earth’s crust has rebounded (isostatic uplift) exposing and creating a series of raised beaches along the spit. Terminal moraines, like the one at Yankee Harbor, are found at the terminus or the furthest point reached by a glacier.
This moraine has ended next to the water and supplied a steady source of material through erosion and wave action for the development of a spit along the harbour's edge. The moraine is the anchour point for the development of the spit as well as forming a portion of the protection to the harbour from the sea's elements. The development of the spit has extended that protection to the harbour.
How Are Spits Formed?
Spits are usually formed when re-entrance takes place by the longshore drift process from longshore currents. When waves at an oblique angle meet the beach, drift occurs. There is a deposit of sediment in a narrow strip in a zigzag pattern moving down the beach. The same waves also cause longshore currents that complement the formation of the spit.
At the re-entrance, the longshore current spreads out or dissipates and not being able to carry the full load, drops much of the sediment which is called deposition. The longshore or littoral drift continues to transport sediment with the help of this submerged bar of deposit into the open waters alongside the beach in the direction the waves are breaking.
This process forms an above-water spit. The formation of spit will continue out into the sea until the water pressure obstructs in the deposition of sand. As it grows, it becomes stable and often fertile; vegetation starts to grow and supports habitation.
The refraction of the wave can occur at the end of a spit. It carries sediment around the end and forms a hook or recurved spit. Refraction of waves in multiple directions may create a complex spit. If waves arrive in a direction that is not oblique along the spit, the growth of the spit will stop, shorten, or eventually destroy.
The sediments from a variety of sources including rivers and eroding bluffs build spits, and the resulting changes affect spits and other coastal landforms such as moraines from receding glaciers. The sea and wind erode these landforms, but if there is a constant supply of sediment from longshore drift, their existence continues. Depending on the supply of sediment or any interruption occurring in the supply eventually create other landforms like an island or a bar, or a lagoon or a tombolo.
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.
Ground zero is at the tip of the Spit, but you can view the Spit from a safe location to answer the questions.
Questions:
1. Estimate the width of the spit?
2. Estimate the length of the spit?
3. What is spit composed of and its structure? Give detail, size, shape, stability, texture.
4. What caused the bend/curve in the end of the spit?
5. How does the spit contribute to making this a better harbour?
6. What type of wildlife did you see?
7. Post a picture in your log with a personal item or hand in picture to prove you were there. View of spit in the background is fine.
[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.