The Earth Story

Sunglint on African River NASA Astronaut Terry Virts took this beautiful photo. He states that it is a sunglint on a river in Angola. Sunglint is the mirror-like reflection of the sun off of the water directly back towards the camera. The color of sunglint depends on the roughness of the water, the angle of the observer, and the angle of the sun; for example, sunglint during sunset will look gold, rather than silver like this one does. The silver-appearance of the river as it cuts through the brown and green landscape certainly makes for a striking image. I can’t help but think that nature is trying to remind us that water is more precious than silver or gold. - RE Photo Credit: NASA References: http://earthobservatory.nasa.gov/IOTD/view.php?id=9072 http://www.livescience.com/45527-sunglint-lake-baikal.html

iamjuliawheeler

Epic shot of canyon and clouds, edge of the island of Tahiti - check out the sunglint on the water

SUNGLINT

The “wine-dark sea” of Homer’s Aegean can only be understood by those who have immersed themselves in its rich translucence in the dark of night – a translucence like that of fine wine. Certainly in this wondrous photo by NASA, the sea is not “wine-dark” but seems a mix of colors of azure to blue to pearly turquoise. These colors are caused by a process of reflection given the name “sunglint.”

Sunglint is created when sunlight reflects off the sea at the same angle that a satellite sensor (or astronaut's eyes) views it. Because the sea is not a flat surface, but covered by minor waves, crossed by flowing currents, swirled by a mix of upwelling waters, its reflection is not seen as a uniform color to the viewing satellite or astronaut. Sunglint is the sea viewed as an irregular mirror surface, the reflection creating ghostly hues.

For scientists, these reflections reveal details of atmospheric circulation and what is, in this photo, atmospheric gravity waves downwind (south in this view) of the Aegean Islands. The large light-areas swirling in the region south of Crete’s high Psiloritis Mountains (reaching 2,456 m) are caused by the irregular flow of wind over the irregular topography, roughening and smoothing the sea surface leeward of the island. Sunglint can obscure other scientific phenomena like areas of phytoplankton and sediment load. But it can also help spot oil floating on the sea surface as the oily film smoothes the reflection locally, and dulls the Sunglint.

Now what, one wonders, would this reflection look like if a thin film floating on the sea’s surface was some of Homer’s wine, not oil?

Annie R

Photo from NASA Earth Observatory: http://earthobservatory.nasa.gov/IOTD/view.php?id=84333&src=fb Speculations on the Wine-Dark Sea from:http://www.nytimes.com/1983/12/20/science/homer-s-sea-wine-dark.html And Psiloritis: http://www.psiloritis-natural-park.gr/Home/2/1.html

Reflected solar orb From the space station, the sun often glints of water on the planet's surface, but usually in sharp flashes as the station speeds along above the surface in its low orbit. Here, unusually, the entire orb is reflected back into space from a body of water. Loz Image credit: Ric Mastracchio

Bengal Fan

The Ganges and Brahmaputra Rivers drain much of the front of the Himalayan Range and systems related to them have been carrying sediment towards the Indian Ocean for tens of millions of years. Offshore of the modern river deltas, an enormous pile of sediment has built up known as the Bengal Fan. Seismic studies show that the pile of sediment is at least 16 kilometers thick, and may be up to 22 kilometers thick (depending on whether the rocks at the bottom are ocean crust or highly metamorphosed sediments). The sedimentary record is so huge it has actually interacted with plate tectonics – a feature called the Ninety-East Ridge on the floor of the Indian Ocean has actually split the fan into different lobes, and some of the sediment from this fan has probably been pulled down the Sunda trench (the subduction zone that runs to the south). This Space Shuttle photo captures the delta that makes up Bangladesh today. As sediment passes through this delta, it flows into offshore canyons where it piles up and eventually avalanches downslope as turbidity currents.

A large fraction of what use to be the Himalayas is found in the Bengal Fan today. Scientists have taken measurements of the properties and chemistry of the fan as a record of the evolution of the Himalayas and the associated Monsoon system – major changes in the sediments in the Fan are thought to be associated with changes onshore.

-JBB

Image credit: http://bit.ly/2foVxIK

References: http://go.nature.com/2wCyVHT http://bit.ly/2vgtX43 http://www.whoi.edu/pclift/BengalSummary.pdf

The video in this is really quite spectacular. Zooms in to waterfalls, overflights of glaciers, really well done.

Seven Sisters over Reunion and Mauritius Karen Nyberg snapped this wonderful image of dusk over the Indian ocean with the Pleiades high overhead from the International Space Station. The thin green band of airglow marks where our protective atmosphere meets the cold empty deeps of space beyond.... Loz

Rock climbing in Norway’s Lofoten Islands produces spectacular views of both the mountains and the fjords below.

This is rather awesome and a bit depressing. The Los Angeles River used to be a wild, ephemeral river - moving across a large floodplain as it flowed from the mountains north of L.A. to the Pacific Ocean. However, a migrating river doesn’t work well in an urban area of 10 million inhabitants and in the 1930s the river was almost entirely paved. You’ve seen it in a variety of movies, I promise. Today, the river still flows in these concrete channels, built with levees to prevent flooding of the nearby structures. This video explores aerial views of that concrete river, including both dry and flowing sections.

The world's widest river.

The misnamed Rio Plata (silver river) occupies what was once a broad river valley that was drowned by rising seas during the melting at the end of the last ice age. The Spanish colonists hoped to find another Potosi inland, and gave it its name in the hope that tonnes more silver would flow down it to enrich Spain. It is about 290Km long, and starts at the confluence of the Rio Parana/Paraguay delta (that flows over Iguazu falls many miles to the north) and the Rio Uruguay. Its funnel starts two Km wide, opening out to about 220 at the Atlantic coast, making it the world's widest river (some dispute this, considering it a marine gulf). It now forms the border between Argentina and Uruguay, flowing above the Precambrian Rio de la Plata craton, and was the site of a major naval encounter in the last world war.

The drainage basin that feeds it is the second largest on the continent, after the Amazon, covering about a quarter of the landmass, starting far to the north in southern Brazil and Paraguay. The sediments on both sides of the river are very different. In Montevideo one has lush golden sandy beaches, at Buenos Aires and its delta suburb of Tigre lush treescapes growing in fine dark mud. This is due to the sediment loads of the different rivers as they pass over different lithologies on their meandering journeys, picking up different types of rock particle along the way. The Parana, in the upper left of the image carries muddy silt, and the Uruguay to the right fine sands. A submerged shoal divides it into freshwater and estuarine brackish water.

Loz

Image credit of the river at sunset: Karen Nyberg.

http://www.atlasdebuenosaires.gov.ar/aaba/index.php?option=com_content&task=view&id=317&Itemid=185&lang=en

Clouds rolling over lake Tahoe, California and Nevada

Internal Solitary Waves

This image taken by the MODIS instrument on NASA’s Earth imaging Aqua satellite, part of its Earth Science fleet. The islands at the center of the frame are Bali to the west and Lombok to the east. The channel between the two, the Lombok strait, has upper and lower segments with different shapes that allow tidal currents to flow through at different rates. Every two weeks, the current flow in these two parts of the channel lines up, leading to an exceptionally strong current flow called an internal solitary wave. The mechanisms for how these combined waves are generated have been a focused topic for research in fluid dynamics over the last decade.

The bright surface of the ocean is illuminated by sunglint – light from the sun reflecting directly at the camera tends to make small surface features including solitary waves and tsunami waves visible to the camera from orbit.

-JBB

Image credit: NASA/Aqua/MODIS https://www.nasa.gov/image-feature/oceanic-nonlinear-internal-solitary-waves-from-the-lombok-strait

Reference: http://www.nonlin-processes-geophys.net/17/633/2010/npg-17-633-2010.pdf http://www.sciencedirect.com/science/article/pii/S0079661113000414