Sea cliffs and seabirds photo by TAZAWA Michihiro

3. Description
3a. Description of property
3a.1 Topography and geology
3a.2 Climate
3a.3 Sea ice
3a.5 Plants
3a.6 Animals
3a.7 Utilization of natural resources

3b. Human history and development
3c. Form and date of most recent records of property
3d. Present state of conservation
3e. Policies and programs promoting the property

Description

3a.4 The marine ecosystem under the sea ice around Shiretoko

3a. Description of property
3a. 1 Topography and geology
The Shiretoko Peninsula is located in the northeastern tip of HokkaidoIsland. The narrow peninsula is approximately 25 kilometers wide at its
base and protrudes 70 kilometers out to the southern boundary of theSea of Okhotsk. It is flanked by the Sea of Okhotsk on the west and theNemuro Strait in the east. A group of volcanoes higher than 1,500
meters above sea level runs along the center of the peninsula including
the highest peak Mt. Rausu (altitude 1,661m). Apart from some marine
terraces, the peninsula is steep with little flat ground between the peaks
and the coastline.

Figure 3-1 Schematic diagram showing the tectonic evolution in the AkanShiretoko area after 4 Ma. (after GOTO , FUNAYAMA, GOUCHI& ITAYA 2000)

Description

The Shiretoko Peninsula was formed by volcanic activities and upliftfrom the Pacific Plate subducting under the North American Plate (e.g.
Goto et al., 2000; Gouchi et al., 1991; Funayama et al., 1993) (Figure 3-1).
At the beginning of tectonic activity there were submarine volcanoes,
followed later by volcanic eruptions on land. From 8.6 million to twomillion years ago, submarine volcanic activities occurred and formed thehyaloclastite layer commonly seen along the coastline today. From twomillion to 250,000 years ago, while there were active submarine volcanicactivities off the tip of the peninsula, volcanic activities also began onland at the base of the peninsula. Later, from 250,000 years ago to today,
the area became a compressive stress field which resulted in thepeninsula being folded and uplifted. In addition, volcanic activities
continued along the anticlinal axis (the central area of the peninsula) (e.g.
Goto et al., 2000).

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2004 WORLD HERITAGE LIST NOMINATION ● JAPANThe Shiretoko Peninsula and the Kunashiri and Etorofu islands areformed in an echelon structure. This is due to a unique geologicalcondition of the echelon folding caused by the oblique subduction of thePacific Plate resulting in the margin of the North American Plate
adjacent to the Kuril trench migrating westwards (Kimura et al., 1986).

Sea cliffs along the coast
photo by Ministry of the Environment

Mt. Iou (altitude 1,562 m) is famous worldwide for erupting large
amounts of highly pure molten sulfur. There have been at least four
eruptions since the 1800s and the volcano is still active. In the eruptionof 1936, the mountain kept erupting molten sulfur for eight months. The
amount of sulfur produced at the time was approximately 200,000 tons
which exceeded the level of annual domestic production (Katsui et al.,1982). A volcano ejecting large amounts of molten sulfur is extremelyrare globally (Goto et al., 1999) and the phenomenon gained worldwide
attention (Watanabe, 1940). The detailed information and photographs
recorded at the time (Watanabe and Shimotomai, 1937) are precious
scientific data. Molten sulfur also spewed from the explosion crater on
the mountainside in the eruptions of 1857-1858, 1876 and 1889-1890.
Fumarole activity still continues and spews volcanic gas and hot water
today.

Description

The contrasting coastlines on the east and west sides of the peninsula
were formed by a combination of volcanic activities and marine erosion.
On the coast facing the Sea of Okhotsk, the deposits of ejecta from morethan one million years ago are eroded by waves as well as sea ice which
resulted in the development of sea cliffs. Especially around Utoro, there
are spectacular sea cliffs ranging from 60 meters to 120 meters inheight consisting of andesite lava from the eruption of Mt. Rausu 80,000
years ago. In contrast, the coastline on the Nemuro Strait side is smooth.
Along this coast, there are curious rock formations that are the result ofdifferential erosion of the hyaloclastite layer (Goto et al., 1990; Goto andGouchi, 1991; Katsui et al., 1985; Shari town and Rausu town, 1999).
As described above, the diverse landscape of the Shiretoko Peninsula
has been developed by various geomorphologic processes such as
tectonic movement, volcanic activity and marine erosion. Furthermore,these landscapes have been preserved undamaged, with human activity
only very minor.

Sulfer from Mt. Iou photo by Shiretoko Museum

3a. 2 Climate
The climate at the elongated Shiretoko Peninsula has two distinct
characteristics due to topographical and geographical conditions. One is
the strong influence of maritime conditions since the Shiretoko
Peninsula borders two seas, the Sea of Okhotsk and the Nemuro Strait.
The other characteristic is the large regional difference in factors suchas temperature and precipitation between the eastern and western partsof the peninsula. This is due to the fact that the precipitous Shiretoko
mountain range of 1,000 meter class are situated along the center of theShiretoko Peninsula dividing it into the eastern and western section(Shari town and Rausu town, 1999).

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The Rausu side which faces the Nemuro Strait receives high precipitation(annual precipitation: 1,600mm) as the humid southeastern winds form thePacific blow towards the Shiretoko mountain range in summer and low
temperatures are frequent due to the development of sea fog (the averagemaximum temperature for August 1998 was 18.9°C). In winter, there isrelatively heavy snowfall but the weather tends to be mild with theinfluence of the maritime climate of the North Pacific (the averageminimum temperature for February 1998 was −10.9°C) (Matsumoto, 1985;
Shari town and Rausu town, 1999; Rausu town, 2001).

Description

On the other hand, the Utoro side which faces the Sea of Okhotsk has
higher temperatures (the average maximum temperature for August
1998 was 21.8°C) with little precipitation in summer (annual precipitation of
Shari town is 813mm) because of the foehn phenomenon caused by thewinds blowing down from the Shiretoko mountain range and of theeffects of the Soya Current, which is the only warm current in the Sea ofOkhotsk (Matsumoto, 1985; Shari town and Rausu town, 1999).
Temperatures are low in winter due to the cold northwestern winds fromthe Sea of Okhotsk. In addition, the sea ice which covers the coastal
waters reflects the sunshine (the “albedo effect”) and intercepts the heatradiating from the sea water to the atmosphere, thereby further
lowering the temperature (the average minimum temperature forFebruary 1998 was −16.1°C) (Aota, 1993; Rausu town, 2001) (Figure 3-2).

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