Seiland


or is a substantial island off Norway's northern coast, covering about. It is the eighth largest island in Norway proper, located in Finnmark county. It sits within the Caledonian orogenic zone, a mountain‑building belt formed during the Paleozoic. The southern and western parts of the island consist mainly of gabbroic rocks, marking the northeastern end of a basic petrographic province that extends more than 100 km to the southwest. The island is divided between the Alta and Hammerfest municipalities.

History

Archaeological remains—from Stone Age and Iron Age habitation sites to nineteenth‑century farm foundations—lie along many fjords, while Sami cultural heritage endures in old reindeer corrals, seasonal huts and sheep pens. In 2006, the majority of central Seiland was designated as Seiland National Park.
There are two glaciers on Seiland: Seilandsjøkelen and Nordmannsjøkelen. The tall Seilandstuva is the tallest mountain on the island. A number of fjords are located on the island including Lille Kufjorden, Store Kufjorden, Nord-Bumannsfjorden, and.

Geography and climate

Seiland is the second‑largest island in Finnmark and is almost bisected by the fjords Store Kufjord and Jøfjord. The meltwater river Melkelva—so called because its heavy load of glacial "rock meal" gives it a milky appearance—flows from the Seilandsjøkelen ice cap across a hummocky outwash plain and drops via rapids and waterfalls into Store Bekkarfjord.
Seiland's terrain is exceptionally rugged, especially in its southern reaches where the land rises abruptly from sea level to the summit of. Many peaks reach between, and the deeply incised fjords and valleys display near‑vertical walls that form cliffs up to high. The island's high latitude and elevation produce a cold, wet climate, and persistent snow fields remain in the interior throughout the year. Two large glaciers occupy the island: Seilandsjøkelen to the east and Nordmannsfjordjøkelen to the west. The western glacier has retreated considerably since 1900, its area halving and its volume declining even more sharply over the past century.

Geology

Geological investigations by the Geological Survey of Norway began in 1952 to evaluate, among other aims, the commercial potential of thick albite‑nepheline pegmatite dykes. Seiland comprises two main complexes: a supracrustal amphibolite‑gneiss complex, characterised by gneissic textures derived from sandstone and overprinted by metasomatic alteration; and a suite of igneous rocks ranging from gabbroic to ultrabasic compositions, including anorthosite, norite, olivine gabbro, pyroxenite, amphibolite, and peridotite, each hosting minerals such as plagioclase, olivine, pyroxene, hornblende and spinel. All gabbroic bodies on the island are concordant, with no discordant contacts, and several exposures exceed in thickness while showing distinctive layering. Such layered mafic intrusions are rare worldwide—examples include the stillwater igneous complex and Bushveld Igneous Complex—but Seiland's gabbro is unique in occurring within a collisional orogen, where internal layering is uncommon. Theories for this layering range from crystal settling under magmatic convection to analogies with crustal stratification, yet the precise mechanism remains under study.
Dykes traverse the island, cutting the gabbroic units and, to a lesser extent, the metamorphic complex. These include basic dykes of various generations and an array of pegmatite dykes whose widths range from to over. Among the pegmatites are granite, syenite, nepheline syenite, ringite, quartz diorite, diorite and gabbroic types. Their extreme compositional diversity suggests multiple origins: only the gabbroic, quartz‑diorite and diorite pegmatites likely derive from differentiation of gabbroic magma, whereas the genesis of canadite and ringite remains enigmatic. The largest known dyke is a heterogeneous canadite body extending westward from Bekkarfjordnes for several kilometres and reaching more than in width.