The Oslo Fjord archipelago is large and diverse. Taking a trip on the fjord you will travel through quiet inlets and coves via huge fjords and out to the outer reefs that have been washed naked by waves from the Skagerrak.
The coast of the Oslo Fjord is many things - depending on who sees it and where it occurs. Furthest out is the fishermen's kingdom. furthest in the agricultural fields, the woods and the farms take over, along with small settlements and cities. All possible transitions and combinations add up to a varied and interesting picture for lovers of nature. Here freedom is found in untouched nature, ocean, waves and fresh winds. And those living, vacationing and working here give both life and movement to the area.e conserve land through outreach, restoration, and research.
Shoreline with pebbles in lovely grey and brown, rocks in glistening orange, beige and grey-black shades, blue sea against the wide horizon. This is how the coast of the Oslo fjord rises into the day. In this beautiful and interesting archipelago: Mølen, Heia, Svenner, Færder, Torbjørnsskjær, Tisler, Bolærne, Verdens Ende, Akerøya, the Søster islands, Struten, Kuvauen, Tønsberg Tønne, Hankø, Saltholmen, the Sletter islands and Jeløy.
Norway's capital Oslo is located at the very inner part of the fjord. This lovely city, which is surrounded by hills, is probably one of very few capital cities that can offer such a wide and diverse range of sights and attractions - all year round!
The mighty Færder, Svenner and Torbjørnskjær lighthouses reminisce of human presence and are guiding mariners. Many sailors and ship's crews have been put to the test in storm and nice weather alike, against the treacherous underwater reefs, currents and breakers, in small and large boats and ships, all year round. The Oslo fjord has had its share of shipwrecks and acts of heroism. Thousands in the fishermen's cottages between rocky outcrops and in ports have been waiting for their loved ones during long stormy nights and days of uncertainty and fear.
The same coastline is also a vacation paradise in the summer, when the sea is calm and tiny waves gurgle against the boats cruising between islets and reefs in the archipelago. Plastic, wooden and sailboats swarm around, headed for fishing spots or a sheltered cove for picnics or sunbathing. Most vacationers at the Oslo fjord keep coming back, time and time again. No one remains untouched by the grandeur and splendor that the archipelago offers, the borderline between ocean and land.
Looking at the rocks, islands, islets and reefs around us, they seem eternally unchangeable and incorruptible. As they are colored red by the setting sun, or when sea foam detaches itself from the grey-blue waves and washes over the cliffs, we think that this is how it always will be. Our presence is but a glimpse in geological history...
Looking at the oldest bedrock (gneiss) along the Oslo fjord we need to go far back in time - 1 billion years! - to find the origin of the Oslo fjord and the surrounding landscape. During this period the south-eastern part of the country went through a troubled time. Land masses began drifting apart and volcanos appeared. Lava from the depths flooded large areas. Far down the lava congealed into rocks with large crystals. During millions of years everything on top of this bedrock was worn away. It was subjected to further wear. 600 million years ago the land was flooded. Norway transformed into a shallow tropical coral sea. 200 million years Oslo, as large parts of the rest of the country, was quite like today's Red Sea or the Great Barrier Reef along Australia's eastern coast. Several kilometers thick layers of sediments consisting of clay and limestones were built up during all this time. These sediments have since been petrified into cambro-silurian bedrock. Several places offer fossils and thus an insight into what the environment was like at the time. All the Oslo islands originates from this period in time.
Weather, wind, ice and water have done their work over millions of years. The last Ice Age, leaving a heavy sheet of ice across Norway, and the weight of the ice pushed the land down. About 11,000 years ago the climate became milder and the ice retracted from the coast. At the same time the sea level rose. The highest peaks along the shores of the Oslo fjord ended up 70 meters below sea level - as deep underwater reefs!
Where the front of the glacier stood still for a while, or where the glacier advanced, large masses of clay, sand and rocks were deposited. These moraines are called "ra" in Norwegian. The large ra going around the south of Norway actually starts in Østfold. Remnants of this ra can be seen on the large pebble beach on the Herføl island in the Hvaler archipelago. Remnants of the glacial moraine are also visually present on some of the other islands. The ra continues across the Oslo fjord south through Vestfold, plunges into the depths of the Skagerrak before it re-appears at the Jomfruland island outside Kragerø, Telemark, before continuing down the coast.
After the Ice Age land masses began to arise, and soon the highest peaks emerged above sea level as islands and reefs. The land has continued to rise, more and more reefs have emerged, washed smooth by the waves, and have been joined together with the mainland and larger islands. Clay and gravel have been deposited in valleys and become the sandy and calcareous soil along the coast of Østfold. The land is still rising, at present approx. 2 millimeters per year, or about 20 centimers per century. In not too many millenniums the Oslo fjord and its islands may become landfast, a future we will not live to see. If the crustal continues at its present pace, Hankø and the Hvaler islands may be connected with the mainland in about 20,000 years. But for the time being we will still have to connect to the mainland by bridges, boats and ferries.
Polished Rocks and Potholes
The coastal landscape of Østfold is beautiful. Here are no high peaks or deep valleys, but in return the polished rocks and islets are ever so inviting. Do not be fooled into thinking that geology is not very exciting. The rock formations you can see jumping ashore on an island or islet, tell us that mighty geologival processes have taken place here. The nice, smooth forms of the rocks are ideal for sunbathing and as resting places for relaxing summer days. Although the rock is hard, it is in a way like silk to the touch. The lines are soft and round. Who wouldn't doze off for a moment with the heat from the mountain on one side, the warming sun on the other, and the sound of the waves in the ears?
Most people know that polished rocks have something to do with the ice sliding over them. Ice and water formed the rocks. The glacier gathered pebbles and rock particles underneath. When it moved over water, sand and gravel, it acted like a gigantic water sander. Ice becomes plastic under pressure. The result is fantastic looking rocks, often with visible scratches from larger stones, called scrubbing stripes.
The reason why we rarely find smooth rocks inland is that the rocks have been covered by vegetation during the last 10-11,000 years. The plants' roots have dissolved the nourishing minerals, while the hard minerals remain. Thus the surface has been roughened over time. Only rocks that have been protected from plant roots have managed to retain their smooth surfaces.Out by the coast, only a "short" time has passed since the land rose, and the rocks have thus been protected by the sea and mud ever since the Ice Age. Today sea spray and harsh weather conditions ensure that there is no vegetation.
You have probably noticed that you always find the sandy beaches on the inner side of the islands while pebble and rocks are left on the outside? The ocean has washed the sand, gravel and small pebbles over the island and left them on the inner side, where the waves are not so heavy. Sand desposits are also found at a few meters depth outside the pebbled beaches. This is sand washed out by the waves and left where the waves don't have the same force as on the surface. But some years they wash the sand back onshore and the result is an exotic, fresh beach.
Potholes are smooth, rounded depressions in the rock and have been made by glacier rivers setting stones and gravel in turbulent motion beneath the ice. The width and depth of potholes range from a few centimeters to several meters. In ancient times people believed that these potholes were created by wizards and giants.
The stone ring field at Hunn is perceived by many as the most spectacular cultural monument along Oldtidsveien. A number of tombs from pre-Roman Iron Age consist of rings of large boulders, and some smaller tombs and mounds, also from the early Iron Age, are scattered over a large area and create a unique atmosphere in this beautiful clearing ing the forest.