Náttúrufræðingurinn - 2019, Síða 45

Tímarit Hins íslenska náttúrufræðifélags
45
10. mynd. Sandleiðin austan Hlöðufells. Sandurinn berst frá gömlum
vatnsbotni og virkum flæðum jökullænunnar Læmis. Leiðin á Rótarsand
er um 16 km löng.38 – A “river of sand”, 16 km long, from the edge of
Langjökull to Rótarsandur sandflat.38 Colours indicate sand cover (%).
jarðar og stærstu auðnir norðurheim-
skautssvæðisins, og tilvist þeirra í röku
og köldu loftslagi. Margar auðnanna
eru afleiðing af samspili ágengrar land-
nýtingar og óblíðrar náttúru. Þar hefur
land „farið í sand“, sem er mjög alvar-
leg tegund vistkerfishruns (11. mynd).
Koma þarf í veg fyrir ágang sands af
fremsta megni og víða þarf að aðhafast
enn frekar við endurheimt landgæða á
sandsvæðum. Á móti kemur að sumar
sandauðnir landsins ættu að njóta sér-
stakrar verndar, ekki síst þær sem eru
á hálendi í nágrenni jökla. Sandauðnir
innan marka Vatnajökulsþjóðgarðs eru
verndaðar eins og önnur svæði þjóð-
garðsins. Söndum mætti gera mun
hærra undir höfði sem náttúrufyrir-
brigði og landslagsheild.
Fjallað er um nokkur virkustu sand-
svæðin enn frekar í annarri grein í þessu
riti síðar á árinu.4 Þar er lögð áhersla
á uppfok, ryk, áfok og áhrif áfoks
á vistkerfi.

ENGLISH SUMMARY
icelANdic sANdy deserts
ANd AeoliAN processes
This paper is one of two reviewing
the nature of sandy deserts and aeolian
processes in Iceland. The sandy deserts
cover >20,000 km2 or about 20% of Ice-
land. They are unique on global scale
because of their composition being
basaltic, poorly crystalized, glassy, vol-
canic materials and dark color, their
large extent, and their existence under
humid cold climates. The sandy sur-
faces are divided into sand fields (Icel.
sandur), sandy lag-gravel, and sandy
lavas. The materials of the sandy deserts
include sand, silt and some clay. The
flux of sand has been measured at sev-
eral locations on different types of sur-
faces, revealing flux from a few kg up to
several tons of materials that are trans-
ported over one m wide line each year
or even in a single storm. The finer pro-
portions of the sandur materials, pri-
marily silt, become uplifted and can be
transported vast distances (see accom-
panying paper, in print).4 Advancing
sand fronts can form where there is
ample sediment supply near vegetated
systems, which can totally destroy fully
vegetated systems in their path. This
has been one of the major forms of eco-
system collapse during the last millen-
nia, with well documented processes
in South Iceland. Sandy materials can
be transported long distances (10’s of
km) from source areas forming unique
“rivers of sand” until reaching an obsta-
cle such as a river or a mountain. It is
important to maintain strong vegeta-
tion cover near active sand sources,
where ash is deposited during volcanic
eruptions and where sandy materials
(sand and silt) are deposited during
major flooding in glacial rivers. Details
on the major dust sources and dust
accumulation in Iceland is given in an
accompanying paper.4