Pirunpesä

Tiirismaan Pirunpesä

Useful Information

Location:	Arvi Hauvosentie 2, 15860 Hollola. Hollola is an eastern suburb of Lahti. Follow Hämeenlinnantie, tunr right towards Messilä 1.3 km, turn left 700m. Tiirismaarundans p-plats. (61.0090748, 25.5360621)
Open:	no restrictions. [2024]
Fee:	free. [2024]
Classification:	Gorge Salpausselkä UNESCO Global Geopark
Light:	n/a
Dimension:
Guided tours:	self guided
Photography:	allowed
Accessibility:	no
Bibliography:
Address:	Pirunpesä, Tel: +358-.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then. Please check rates and details directly with the companies in question if you need more recent info.

History

19th century	becomes a tourist destination.
1960s	declared a Natural Monument.
1970	Pirunpesä nature reserve established.

Description

Pirunpesä (Devil’s Nest) is one of several dozen sites with that name. Most are caves or Geology potholes, this one is a gorge which cuts through the quartzite rocks of Tiirismaa hill (223 m asl). Hence, it is also known as Tiirismaan Pirunpesä (Tiirismaa Devil’s Nest), sometimes it is named Pirunpesä Hollola (Devil’s Nest Hollola) after the nearby suburb of Lahti.

The gorge was formed along a weak zone in the Tiirismaa bedrock by erosion. The melting waters of the glacier some 12,000 years ago created a huge lake north of Tiirismaa cliffs. At one point the water of the ice lake started to flow out across the weak zone in the bedrock, which was eroded faster than the surrounding rocks. Very fast the gorge was created, a result of the enormous amount of water in the lake, which was fed for some time by the melting glacier. While the fine material was transported away by the river, the huge boulders were deposited at the southern end of the channel. Here the river was not restricted by the walls of the gorge any more, it widened and thus lost much of its energy. So it was not able to transport the heavy boulders further. The result is a quite spectacular boulder deposit.

At the southern end the gorge is between 15 m and 20 m wide and forms a sort of widening. Here the floor is covered by massive boulders. After about 30 m climbing the boulders an extremely narrow section is reached, which about 5 m wide and 20 m deep. This is the most spectacular part of the gorge. And the only way to reach it is by squeezing through a narrow section, where the 5 m wide gorge is almost completely blocked by a boulder. So the path is only 30 cm wide. The narrow section of the gorge is about 70 m long, then it widens again. The gorge has a sort of funnel, where the water from the lake entered the gorge.

The bedrock is quartzite, which is sandstone of quartz grains which were glued together by a matrix of quartz. In other words, the rock is almost entirely composed of quartz. As quartz is resistant to acids, and the structure of the sandstone makes it much less brittle, this is one of the most weather-resistant rocks. The quartzite here is 1.84 Ga old, so it is of Precambrian age.

The gorge is part of Tiirismaa nature reserve and a geosite of the Salpausselkä UNESCO Global Geopark, and has a size of 34 ha. The slopes of Tiirismaa hill are crisscrossed by a network of hiking trails. The basic trail is 4.5 km long and starts at the Arvi Hauvonen Road and ends at the Tiirismaa radio mast.