This treasure was left behind in front of melting glaciers when warmer times came to Modalen at the end of the Ice Age about 11,000 years ago. Surging meltwater rivers deep under the ice carved into the moraine deposits and brought sand, stones and gravel to the glacier front. The glacier front stopped several times as it melted back along the long and flat valley. This is how several of the glacier's lateral moraines were deposited. Some of the sediment masses were tipped into the fjord. At its longest the fjord reached all the way to Hellandsfossen Waterfall, when the sea was 50 metres higher than today. Other deposits were left behind on the large river plains in front of the glacier. Now, the sediment masses lie on dry ground, including those that were deposited in the fjord. Mo-inhabitants can thank uplift of the land after the Ice Age for this.
The mountain that Modal Glacier carved into is made of gneiss that includes a lot of quartz and feldspar minerals. Especially the amount of quartz increases the quality of the sand. Softer minerals, such as mica and amphibole, were crushed into fine-grained silt and clay that has been deposited at the bottom of the fjord in front of the glacier. The low amounts of iron and hummus in the sand enable it to meet the strict requirements of sand to be used for mixing cement.
Most of the sand has been removed from Mostraumen and Mo. For a century sand vessels transported sand to the Bergen area. But, from Nedre Helland and up along the valley there is still a lot left. Regardless, the sand quarrying will one day come to an end - the glacier's gift cannot renew itself. Nor is there sand and gravel in all of the mounds in the valley. In some places gravel quarries were opened before the deposits were sufficiently examined. At Nedre Helland there are two deposits, but only one of them was shown to be usable. The other is abandoned and appears as an open wound in the landscape (frame). The landowners that have now taken over the sand quarry operate according to current regulations and even out and plant the old sand pit so that it can be used for grass production.
