August 7th, 2009 Category: Snapshots

California, USA - July 3rd, 2009

Water currents in the Pacific Ocean off the west coast of California make interesting patterns as they swirl around Point Reyes (top) and out of the San Francisco Bay (right).

Point Reyes is a prominent cape in Marin County approximately 30 mi (48 km) west-northwest of San Francisco. The term is often applied to the Point Reyes Peninsula, the region bounded by Tomales Bay on the northeast and Bolinas Lagoon on the southeast. The headland is protected as part of Point Reyes National Seashore. In this orthorectified image, Inverness Ridge can be seen running along the peninsula’s northwest-southeast spine.

To the southeast, the city of San Francisco glows at the northern end of the San Francisco Peninsula, with the Pacific Ocean to the west and San Francisco Bay to the east. The Golden Gate Bridge can be seen connecting the peninsula to the Marin Hills in southern Marin County.

Part of the San Francisco-Oakland Bay Bridge (to the right of the Golden Gate) and the Richmond-San Rafael Bridge (above the Bay Bridge) can also be seen.

Tags: California Currents Golden Gate Bridge Marin County Marin Hills Pacific Ocean Point Reyes Richmond-San Rafael Bridge San Francisco San Francisco Bay San Francisco Peninsula San Francisco-Oakland Bay Bridge |  Print This Post |  Email This Post | | Leave a comment

July 26th, 2009 Category: Volcanoes

Italy - July 1st, 2009

Wind and water currents, as well as passing ships, create different patterns in the Strait of Messina and the Mediterranean Sea, between Sicily and mainland Italy.

Onland, another interesting feature of this orthorectified image includes the  Mount Etna volcano (lower left), whose flanks are covered in fertile volcanic soil that supports extensive agriculture. The sides of the volcano appear smoother in contrast with the mountains and hills to the north.

Tags: Currents Europe Italy Mediterranean Sea Mount Etna Orthorectification Sicily Strait of Messina |  Print This Post |  Email This Post | | Leave a comment

July 26th, 2009 Category: Snapshots

Cape Verde - July 1st, 2009

Santo Antão (above) is the westernmost and largest of the Barlavento islands of Cape Verde. The nearest main island is São Vicente to the southeast, separated by a channel named Canal de São Vicente. The lines in the water in and near this channel indicate that the current is moving westward, around the islands.

The island is entirely made up of volcanic material. The island is divided into north and south by a mountain range, whose peaks can be seen clearly in this orthorectified image. The tallest mountain is Topo de Coroa, reaching a height of 1,979 m. The second tallest is Pico da Cruz at 1,585 m.

São Vicente (below), also belonging to the Barlavento islands group of Cape Verde, is roughly rectangular in shape with a surface area of about 227 km2 (88 sq mi). From east to west it measures 24 km (15 mi) and from north to south no more than 16 km (9.9 mi).

Although volcanic in origin, the island is quite flat. Its highest point is Monte Verde, located in the northeast-central part with an altitude of 725 metres (2,380 ft).  Other mountaintops include Monte Cara and Topona. Although a great amount of erosion has taken place, some craters still remain — in particular near the bay of Mindelo.

Tags: Barlavento Islands Canal de São Vicente Cape Verde Currents Monte Cara Monte Verde Orthorectification Pico da Cruz Santo Antão São Vicente Topo de Coroa Topona |  Print This Post |  Email This Post | | Leave a comment

June 17th, 2009 Category: Snapshots

Greenland - June 7th, 2009

Part of Greenland’s eastern coast is visible here, bordered by the Greenland Sea. All towns and settlements of Greenland are situated along the coast, although the population is concentrated along the west coast.

Here, changes in ice solidity create swirled patterns in the sea. This arm of the Arctic Ocean is the ocean’s main outlet to the Atlantic. The progressively colder waters of North Atlantic Current sink in the Arctic Ocean, returning south in the form of cold East Greenland Current, an important part of the Atlantic conveyor belt.

Tags: Arctic Ocean Currents Greenland Greenland Sea Ice |  Print This Post |  Email This Post | | Leave a comment

June 4th, 2009 Category: Volcanoes

Aeolian Islands and Sicily, Italy - May 11th, 2009

The Aeolian Islands or Lipari Islands are a volcanic archipelago in the Tyrrhenian Sea north of Sicily.  Above, in the full image, the spiralling shape of currents in the sea is visible.

The largest island is Lipari (in the thumbnail image, the fourth from the left edge). The other islands include Vulcano, Salina, Stromboli, Filicudi, Alicudi, Panarea and Basiluzzo.

The present shape of the Aeolian Islands is the result of volcanic activity over a period of 260,000 years.

There are two active volcanoes – Stromboli (in the full image, the island farthest north) and Vulcano (to the right of Lipari). However, most of the islands experience volcanic activity from steaming fumaroles and thermal waters.

Below, on the island of Sicily, the famous Mount Etna volcano can also be observed. As this image has been orthorectified, the volcano and the mountains and hills in this area can be seen without geometric distortion.

Tags: Aeolian Islands Alicudi Basiluzzo Currents Europe Filicudi Lipari Lipari Islands Mount Etna Orthorectification Panarea Salina Sicily Stromboli Tyrrhenian Sea Volcanoes Vulcano |  Print This Post |  Email This Post | | Leave a comment

June 3rd, 2009 Category: Image of the day, Lakes

Apulia, Italy - May 11th, 2009

This ASAR (radar) image makes it possible to observe the direction of currents in the Adriatic Sea around the coast of the Promontorio del Gargano peninsula in Apulia, Italy.

The peninsula’s mountain, Monte Gargano, is visible without geometric distortion in this orthorectified image.

Below the peninsula, the city of Foggia is visible on flatter ground, as is the city of Bari on the coast on the far right.

Several bodies of water can also be seen near the coast west of Monte Gargano, including Lake Lesina (left) and Lake Varano (right).

Lake Lesina is the ninth largest lake in Italy and the second of the southern part of the country. It is about 22 km long, an average of 2.4 km wide and covers an area of 51.4 km².

Two canals, Acquarotta and Schiapparo link it to the Adriatic Sea, from which it is separated by a dune known as Bosco Isola, between 1 and 2 km in width and 16 km in length.

Lake Varano, which is actually a lagoon, has a surface area of about 60,5 km², making it the largest coastal lake in Italy and the largest lake in the south of the country. Its depths range from 2 to 5 meters as one gradually moves away from its center.

Like Lake Lesina, it is separated from the Adriatic Sea by a very thin line of earth, which is about 10km long and 1km wide and covered with pines, eucalyptus trees and other plantlife.

Tags: Acquarotta Canal Adriatic Sea Apulia Bari Bosco Isola Currents Europe Foggia Gargano Peninsula Italy Lake Lesina Lake Varano Monte Gargano Orthorectification Promontorio del Gargano Schiapparo Canal |  Print This Post |  Email This Post | | Leave a comment

March 23rd, 2009 Category: Snapshots

Laguna Madre, Gulf of Mexico - March 19th, 2009

The Laguna Madre is the name of two long, shallow bays along the western coast of the Gulf of Mexico in the United States and Mexico; the two being separated by the outlet of the Rio Grande.

Meaning “mother lagoon” in Spanish, the Laguna Madre proper is 130 miles (209 km) long, the length of Padre Island. Its biological corridor, though, extends well into Mexico, to the mouth of the Río Soto la Marina in the state of Tamaulipas.

In the United States, the section visible here, Laguna Madre is separated from the Gulf of Mexico on the east by Padre Island, and bounded on the west by mainland Texas, and extends from Corpus Christi in the north to Port Isabel in the south.

In Mexico, Laguna Madre is separated from the Gulf of Mexico on the east by a number of barrier islands, including Barra Los Americanos, Barra Jesús María, and Barra Soto la Marina. It is bounded on the west by mainland Tamaulipas.

The Laguna Madre is very shallow, with an average depth of only 0.9 m. It is connected to the ocean by only two narrow inlets, so the tidal range – which is already minor in this part of the Gulf of Mexico – is negligible.

Oceanographically, the Laguna Madre is considered a hypersaline lagoon; this indicates that it is usually much saltier than the ocean, due to being nearly landlocked in a semiarid environment, and is one of only six hypersaline lagoons in the world. The Laguna Madre has been experiencing a persistent algal bloom (including drift algae) that may be partially caused by its hypersaline conditions, which favor algal growth.

Atmospheric effects are much more important than tides in its circulation; its weak currents generally follow the prevailing winds, and these winds can influence the water level by as much as a meter. Some such currents are visible to the South, their movements made visible by green algae.

Tags: Algal Bloom Corpus Christi Currents Gulf of Mexico Laguna Madre Mexico Padre Island Tamaulipas Texas USA |  Print This Post |  Email This Post | | Comments (1)

March 1st, 2009 Category: Snapshots

Ice melting off Antarctica coast - February 18th, 2009

A network of cracks can be seen in ice in Antarctica (center right). These cracks, called leads, open when warmer conditions cause the ice to break apart, and refreeze when colder conditions are present.

The white swirls in the water are caused by ice forming in the presence of eddy-currents. These currents move in the opposite direction of normal water flow. As ice forms on the surface, it takes on the shape of the currents, making their movements visible to the naked eye.

Tags: Antarctica Currents Eddy-currents Ice Leads |  Print This Post |  Email This Post | | Leave a comment

February 18th, 2009 Category: Snapshots

Currents near Antarctica - February 15th, 2009

Swirled patterns are visible in currents off the coast of Antarctica.

The lighter grey areas are actually ice that is beginning to form, taking on the swirled shape of the currents.

The currents themselves swirl due to eddy-currents: water flowing in the opposite direction of that of the normal currents.

Tags: Antarctica Currents Eddy-current Ice |  Print This Post |  Email This Post | | Leave a comment