Mining at Poleg Lake EarthCache

Scroll down to read the cache's description in English.

In order to log this cache:

1. Measure the height of the cliff overlooking the lake. You can do this using your GPS by taking two elevation measurements:
   • At the cache location: This is the top of the cliff.
   • At the waypoint: You can approach the water here (please don't enter).
   • What is the difference in heights?
2. Unlike most swamps and seasonal lakes in the area, Poleg Lake is full year-round. Why is that? If you walk around the lake you will find a diagram at one of the lookout decks that explains this. It's in Hebrew but you'll likely understand it regardless of the text.
3. Send me a personal message with your answers to these two questions. You don't have to wait for a reply in order to log your find.
4. Upload with your log a photo of the lake taken from one of the lookouts. One of the following should be in the photo: Yourself, your GPS, or a recognizable personal item.

Information:

Kurkar, a testament to the shifting sands of time, is a unique sandstone formation found from Sinai up to Turkey and primarily along the Mediterranean coastline of Israel. These ridges are the remnants of ancient sand dunes, brought down from the Nile basin and carried north by coastal currents.

Over millennia, the forces of nature transformed these dunes into rock. Calcium carbonate from seashells and other marine life acted as a natural cement, binding the sand grains together in a process known as lithification.

Lithification is the natural process by which loose sediments are transformed into solid rock. It's essentially the glue that binds all the separate particles of sand, mud, and other bits of debris together over time:

• The first step is compaction. Imagine a pile of loose sand. As more and more sediment gets deposited on top, the weight presses down on the lower layers, squeezing them together. This forces out water and air that fills the spaces between the grains, making the sediment denser.
• The second step is cementation. Minerals dissolved in water seep through the gaps between the sediment particles. These minerals then crystallize, acting like glue and binding the grains together into a rock. Calcium carbonate from seashells is the common type of cementing agent that helps form rocks like sandstone.

Lithification is a slow and gradual process that can take millions of years. It's what takes those ancient sand dunes and turns them into the Kurkar ridges we see today. There can also be other processes involved, like the dissolving and re-crystallization of minerals within the sediment. But compaction and cementation are the main actors in this rock-making play.

The Poleg region comprises three Kurkar ridges, formed during the Pleistocene epoch, which spans approximately over the last 2.5 million years. The formation of each ridge corresponds to a distinct ice age. As global temperatures decrease and sea levels recede, leaving a ridge behind. Between each pair of ridges, troughs are formed, which retain water and provide the necessary conditions for the development of swamps.

The soft, porous nature of Kurkar has made it a valuable building material throughout history. Structures built by the Crusaders in the 11th and 12th centuries still bear witness to its durability. In modern times, Kurkar continues to be a popular choice for its warm, natural tones and the ease with which it can be worked. In fact Poleg Lake itself was formed at the bottom of a Kurkar mine which was active until roughly 50 years ago.

Beyond their practical uses, Kurkar ridges also play a crucial role in the region's ecology. These formations provide a unique habitat for diverse plant and animal species, some of which are endemic to the area. The porous rock offers a haven for plant roots and burrowing creatures, creating a vibrant, if sometimes fragile, ecosystem.