We decided on our holiday in Iceland to place an EarthCache at this magnificent waterfall since there isn't one yet. We had lots of fun doing EarthCaches in Iceland and really enjoy to look at these special holiday pictures :) We hope this will also be the case for you here.
Hengifoss: Hengifoss is one of the highest waterfalls in Iceland (the river Hengifossá falls 118 m here). But even more stunning than the high waterfall may be the rock face behind Hengifoss. Like many waterfalls, Hengifoss came into existence during the last ice age. A mighty glacier was moving towards the sea and deepened the valley significantly due to its heaviness. Smaller glaciers in the adjacent valleys could dish only to a smaller extent. After the ice age the glaciers melted, so at the junctions of the side valleys to the main valley a stepped fall remained. As the rocks at Hengifoss are rather hard, the water could not excavate into it, but a waterfall was formed. Due to a number of volcanic eruptions, different layers were formed. Question 1 is related to these layers.
On your way up to Hengifoss you will come past some really interesting rock formations - do not miss the stunning nearly perfect basalt columns of Litlanesfoss!
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey.The word "Basalt" is derived from Late Latin basaltes, misspelling of L. basanites "very hard stone".
Columnar basalt During the cooling of a thick lava flow, contractional joints or fractures form. If a flow cools relatively rapidly, significant contraction forces build up. While a flow can shrink in the vertical dimension without fracturing, it cannot easily accommodate shrinking in the horizontal direction unless cracks form; the extensive fracture network that develops results in the formation of columns. The topology of the lateral shapes of these columns can broadly be classed as a random cellular network. These structures are often erroneously described as being predominantly hexagonal. In reality, the mean number of sides of all the columns in such a structure is indeed six (by geometrical definition), but polygons with three to twelve or more sides can be observed. Note that the size of the columns depends loosely on the rate of cooling; very rapid cooling may result in very small (<1 cm diameter) columns, while slow cooling is more likely to produce large columns (source: Wikipedia).
Similar basalt columns in Iceland can be found at Svartifoss, Kirkjubaejarklaustur and several other places. There are EarthCaches you may want to visit as well. :)
The coordinates are just for your orientation, you do not necessarily need to stand at the exact coordinates. Enjoy the view on lake Lagarfljot where a worm monster (just like Nessie in the Scottish lake Loch Ness) is believed to live in :)
To log this EarthCache, please answer the following questions.
Have fun!
Question 1: How many red layers can you see in the rock face behind Hengifoss? What are these layers made of?
Question 2: When you approach the waterfall, you can hear the sound of the water falling even from far away. Describe what this noise sounds like to you.
Question 3: What is the so called Surðarbrandur bed, which can be found lower in the gorge beneath the waterfall, made of?
Please send the answers to the questions to hengifoss.earthcache@googlemail.com. You don't have to wait for our reply before logging your visit, but please make sure you send the answers first. If no answers are sent to us, we will contact you once, but then soon delete unanswered logs. Additional logging request: We would be very happy to see a photo of you and/or your GPS in front of the Hengifoss. This is optional - it is definitely not mandatory to upload a picture. We ourselves enjoyed taking these pictures at EarthCaches 
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If you find a book here, this is not a logbook of our EarthCache! It is a summit register of Hengifoss. Please do not leave any trading items there...
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