The Emerald River EarthCache

The Julian Alps, the mountain range covering a large part of the Triglav National Park, mainly consist of limestone (Upper Triassic and Liassic platform carbonates), which is responsible for the formation of high-altitude karst forms such as karren, potholes, abysses and pits and caves with watercourses functioning as underground connections of karst lakelets.

In the Pleistocene era, glaciers formed an ice cap over the Julian Alps (which are relatively low in height compared to other regions of the Alps), and drained into the foreland along glacial and fluvial valleys. Owing to Quaternary tectonic activity, fluvial erosion and mass movements of sedimentation, the glacial sediments have been almost entirely removed in some places. Quaternary sediments are represented by partly lithified glaciofluvial sediments, overlain by lacustrine chalk. During the Holocene era, the chalk was partly eroded (in some areas totally) and covered by glaciofluvial sand and gravel which are weakly cemented in some parts into conglomerate and by unconsolidated moraine (till).

The Triglav National Park is famous for its hydrological assets, such as the main watercourses of the Soča, Sava Bohinjka and Sava Dolinka, and numerous torrents. The rivers have cut deep into the surface, carving picturesque ravines, gorges, canyons and troughs. The Soča is a 138-kilometre (86 mi) long river that flows from its source in Trenta, through the Triglav National Park in western Slovenia then onwards through northeastern Italy towards the sea. The Soča is a typical torrential river with big variations in water flow. It has a glacial-fluvial regime in the upper flow and a fluvial-glacial regime in the lower flow. The course of the Soča River can be divided into 3 sections:

• Upper Soča Valley: from its source to Most na Soči where the river flows in its natural course,
• Middle Soča Valley: from Most na Soči to the Slovenia/Italy border where 3 major dams and accumulating lakes are regulating the river,
• The lower Soča: from border to its mouth where the river is freely flowing on north Italian flats.

The width of the river is controlled partially by the lithology (general physical characteristics of the rocks in a particular area) of the bedrock. The Soča is famed for its colour, clear water and its unique trout species Salmo marmoratus (known as the marble trout). The area was awarded the ‘European Destination of Excellence’ in 2008 by the European commission.

Please use observations and research to answer the following questions:

1. Stand on the bridge, facing upstream. Describe the characteristics (shape, texture) of the large rock in the water next to the left (west) bank of the river. What is the type of rock and how was it formed?
2. Describe the colour of the water. What is the geological reason for this water colour?
3. What is the width of the river at this point?
4. Which of the three sections of the Soča (Upper, Middle or Lower) is this point at the river? How does the geology of this section affect the river in this section?
5. What height above sea level is this part of the river? How far has it descended from its source?
6. And finally… to prove you have visited the location… how many wooden boards are there on the footbridge across the river?

Please send answers to me by email. Any logs that are not accompanied by an email with the correct answers will be deleted. Please do not post any photographs of the features mentioned in the questions (photographs of the surrounding area are welcomed though).