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Archive for October 23rd, 2009

Lakes Trasimeno and Bolsena, Italy

October 23rd, 2009 Category: Lakes

Italy - September 24th, 2009

Italy - September 24th, 2009

Sediments swirl in the Adriatic Sea off the east coast of Italy. Located near the center of the shoreline visible here is the port city of Ancona. Moving southwest across the Apennines, two lakes are visible: the green Lake Trasimeno and the dark blue Lake Bolsena.

Lake Trasimeno (or Trasimene) is the largest lake on the Italian peninsula south of the River Po, with a surface area of 128 km², slightly less than Lake Como. Trasimeno is surrounded for half of its shores by hills.

The Tiber River flows some thirty kilometers to the east of the lake, but the lake and the river are separated by hills: no major river flows directly into or out of Lake Trasimeno, and the water level fluctuates significantly according to rainfall levels and the seasonal demands from the towns, villages and farms near the shore.

Lake Bolsena, on the other hand, is a crater lake of volcanic origin, which was formed starting 370,000 years ago following the collapse of a caldera of the Vulsini volcanic complex into a deep aquifer. The lake is supplied entirely from the aquifer, rainfall and runoff, with one outlet at the southern end.

The lake has an oval shape typical of crater lakes. The long axis of the ellipse is aligned in a north-south direction. The bottom is roughly conical reaching a maximum depth at a point in the middle. The entire lake is surrounded by hills on the flanks and summits of which are the comuni. Elevations on the north of the lake are the highest, with a maximum of 702 m (2,300 ft).

Lava Fields and Agriculture on the Snake River Plain, Idaho, USA – October 23rd, 2009

42.9N 112.6W

October 23rd, 2009 Category: Image of the day, Rivers, Volcanoes

Idaho, USA - July 26th, 2009

Idaho, USA - July 26th, 2009

Both circular and rectangular fields follow the path of the Snake River on the Snake River Plain, in southern Idaho, USA. The large lake is the American Falls Reservoir, created by the dam of the same name.

The dam and reservoir are a part of the Minidoka Irrigation Project on the Snake River Plain and are used primarily for flood control, irrigation, and recreation.

The darker brown areas that differ from the otherwise tan terrain of the uncultivated parts of the plain are lava fields. The largest of these is Craters of the Moon National Monument and Preserve, which encompasses three major lava fields and about 400 square miles (1,036 km2) of sagebrush steppe grasslands to cover a total area of 1,117 square miles (2,893 km2).

All three lava fields of Carters of the Moon lie along the Great Rift of Idaho, with some of the best examples of open rift cracks in the world, including the deepest known on Earth at 800 feet (240 m). There are excellent examples of almost every variety of basaltic lava as well as tree molds (cavities left by lava-incinerated trees), lava tubes (a type of cave), and many other volcanic features

The second largest lava field on the Snake River Plain, in the upper right quadrant, is Hell’s Half Acre lava field. It is the youngest of the eastern basaltic lava fields of the plain, and covers an area of about 400 km2.

The lava is basaltic in nature which formed a broad, low shield volcano with dominantly pahoehoe flows that were erupted from a 3 km long, north-west to south-east trending vent system at the north-west part of the field during a brief eruptive episode about 5,200 years ago.

The High Coast of Sweden

63.0N 18.5E

October 23rd, 2009 Category: Snapshots

Sweden - September 24th, 2009

Sweden - September 24th, 2009

The High Coast (called Höga kusten in Swedish) is a part of the Swedish coast on the Gulf of Bothnia, situated in the municipalities of Kramfors, Härnösand and Örnsköldsvik. It can be identified in this orthorectified image as the part of the shoreline extending northward from just below the E-shaped land formation at the center right.

The High Coast is notable as the “type area” for research on isostasy, in which the land rises as the weight of the glaciers melts off of it. This phenomenon was first recognised and studied there; since the last ice age the land has risen 800 m, which accounts for the unusual landscape with tall cliff formations.

Smoke from Wildfires in Several Areas of Queensland, Australia Blows Westward

15.2S 143.0E

October 23rd, 2009 Category: Fires, Lakes

Fires in Australia - October 22nd, 2009

Fires inland

Fires inland

Fires near west coast

Fires near west coast

Fires near Lake Dalrymple

Fires near Lake Dalrymple

Wildfires are burning in several places in Queensland, Australia. The main image gives an overview of the area, including the Great Barrier Reef off the east coast. The smoke from all of the fires is blowing to the west.

The close-ups focus on the locations of various blazes. One shows several plumes of smoke blowing towards the Gulf of Carpentaria from fires near the west coast of the Cape York Peninsula.

Another shows fires and smoke further inland, at the base of the peninsula. The last depicts blazes near Lake Dalrymple, closer to the east coast and south of the peninsula.