iceland lies over a plume of hot material up-welling from great depths and the mid-atlantic ridge, the boundary between the north american and eurasian tectonic plates where new crust is being created on the order of 45 cubic km per 1000 years.

the island nation is one of the few places on earth where you can see an active spreading ridge above sea level with the two plates moving apart about 1 to 2 cm per year. as a result, there is volcanism from well-known volcanoes like hekla, krafla, and surtsey and from enormous fissure eruptions like eldgjá (fire chasm, ~934ad) and laki (skaftar fires, 1783-1784) as well as earthquake activity.

new crust is broken down into smaller particles and into new minerals by processes of physical (i.e., wave action, glaciers, wind, rain, plants, thermal contraction) and chemical weathering (i.e., alteration of volcanic glass).

fresh- to saline-water geothermal systems with temperatures ranging from warm to super-critical are associated with the volcanism. geothermal energy provides about 50% of iceland's energy needs. glaciers cover about 11% of iceland. they provide a glimpse into the pleistocene environment that existed in europe and north america 10,000 years ago.

sub-glacial volcanic eruptions periodically cause large melt-water floods known as jökulhlaup. iceland has also been the focus of studies on climatic change produced by changes in solar output and by large volcanic eruptions. iceland (874ad) and greenland (985ad) were colonized during a period of high solar output known as the medieval warm period that reached a maximum around 1000ad. by 1200ad, the warming trend had culminated, climatic extremes were the norm, and sea ice and glaciers increased.

the little ice age from 1560 to 1890ad was a period of cold and severe winters and short and wet summers. the cloud of sulphuric acid aerosols from the ~934ad eldgjá and 1783-1784 laki volcanic eruptions most likely produced the exceptionally cold winters in europe and elsewhere after these eruptions. the 18th century marked the most tragic era in iceland's history due to climatic change, crop failure, epidemics, farm and fisheries mismanagement, livestock loss, and volcanic eruptions. around one-quarter of the population died in the 1707-1709 smallpox epidemics (lacy 1998). the 1780's were the coldest decade in iceland from 1501-1801 (ogilvie 1995). following the laki eruption, crop failure, the loss of most livestock, and harsh weather contributed to a famine that killed nearly one-quarter of the population.