Rocks and Gorges
The special features of the park include two rift valleys, which have been formed 150-200 million years ago by displacement of the earths crust. Helvetinkolu Gorge, located northeast of the Lake Iso Helvetinjärvi, is the most famous gorge in the area. It is narrow, only a couple of metres wide cleft, which descends steeply to the lake side.
Lakes Kovero, Luomajärvi, Iso Helvetinjärvi, Pikku Helvetinjärvi and Pitkä Helvetinjärvi form a narrow steeply sided chain in the deepest fault, north of Helvetinkolu Gorge. At their highest points the fault-line scarps reach a height of 180-210 metres above the sea level. At some places the sheer cliff faces of the lakeshores rise up to tens of metres from the lake water level.
Many Different Cliff Types
The vegetation on the cliffs of Helvetinjärvi is lush and diverse. The most spectacular sights are on the north side of Helvetinkolu in the area around the lake that has formed there. The tops of cliffs, steep slopes, rock shelves, crevices, the bottoms of rock walls and cavities each have their own characteristic type of vegetation. As well as the type of surface they grow on vegetation is effected by the direction in which it faces, sunlight and shade, how it is sheltered by cliffs, the type of rock it is growing on and how much run-off water the growth spot gets. For these reasons one cliff-side is not likely to have one uniform type of vegetation but different plant colonies right next to each other. By this reasoning the number of species in the area could be larger, but the cliffs are rugged and have few nutrients, which makes it impossible for more demanding species to survive there.
Reindeer lichen and shrubbery typically cover the tops of cliffs. The smaller types of reindeer lichen Cladonia rangiferina and Cladonia arbuscula are more dominant that the larger sized Cladonia stellaris, but there is also room for the Blueberry and the Ligonberry and some mosses such of the Dicranum and the Red-stemmed Feather-moss. The grainy and prickly surface of lichen rugs are interesting to observe, but at the same time visitors should respect that it is fragile and the surface should not be disturbed.
Other species are dominant on steep cliff faces. Skull Lichen and crustose lichens thrive on sunny rock walls. Even dry spells which last several months will not damage skull lichen as it is effective at storing up water from the dew that gathers on it in the morning hours. The lichens do not however dominate the rock faces alone as the Black Rock Moss for example grows along the cliff walls. Paraleucobryum longifolium and other mosses grow on the shady side of the cliffs in the shelter of spruce forests, where there are few if any lichen.
Predominantly on the cliffs which are shaded there is also a phenomenon of “dripping moss”, which means moss grows down the side of rock walls in a slithering way. It can then detach itself from the surface in large patches. Types of moss which may grow this way are feather moss, dicranum and spaghnum moss. The most common moss in cliff crevices is the deliciously named Apple Moss.