The Earth Story

Watch how the clouds sometimes punch through to a higher layer in the atmosphere - that’s the part where it becomes a “pyrocumulus”, the cloud is going so high under its own energy that it begins condensing water and forming a normal water cloud.

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Submarine canyons

The waters of the Earth’s oceans hide many fascinating features. This image shows the topography offshore of the city of Los Angeles.

Like many areas of the world, the area just offshore is shallowly sloped and part of the continental crust, an area known as the continental shelf. That continent ends at a sharp break known as the continental slope, which slopes more steeply down toward the open ocean. At this boundary off Los Angeles, giant canyons have been cut. These are remnants of the recent glaciations. Sea level was lower, exposing parts of the continental shelf. Rivers including the San Gabriel River and the Santa Ana River migrated along these shelves, eroding into them and fixing their position in the form of these canyons. When the most recent glaciation ended, the oceans returned and submerged the canyons, leaving them stranded and hidden from view.

Despite being beneath the waters, these canyons still are active. Sediment carried by rivers to the ocean accumulates at the canyon heads and on occasion that sediment will tumble down, forming submarine avalanches and deposits of turbidites at the base. Similar canyons are found at the intersection between river valleys and the continental slope around the world, a remnant of the Pleistocene glaciations.

-JBB

Image credit: http://commons.wikimedia.org/wiki/File:Canyons_off_LA.jpg

Read more: http://www.nrdc.org/oceans/canyons/ http://www.britannica.com/EBchecked/topic/570847/submarine-canyon http://sanctuarysimon.org/regional_sections/submarineCanyons/overview.php

Owens “Lake”

15,000 years ago, huge glaciers carved great valleys through California’s Sierra Nevada Mountain range. Moisture from the Pacific Ocean is rung out of the air as snow that falls at the range's peak, causing glaciers to flow both east and west from the crest of the range.

East of the Sierra Nevada sits Owens Valley, which receives very little rain because of the mountain range in the way. When the mountains were filled with glaciers, meltwater from those ice sheets fed huge streams and lakes that flooded the low ground from Owens Valley all the way to Death Valley.

Once the glaciers departed, Owens Valley converted into mostly a desert. It receives very little rain, but some streams are fed from snows and rains in the mountains. One of these, Owens River, flowed downhill from the tip of Owens Valley to a flat basin where it formed a lake known as Owens Lake.

That all changed in the early 20th century. The city of Los Angeles constructed an aqueduct that took the water flowing into Owens Lake, causing the lake to rapidly dry up.

Earlier we covered Iran’s lake Urmia, a brewing natural disaster that has shrunk by 88% in the last few decades (http://on.fb.me/1BvJUjE). After the city of Los Angeles took the water, Owens Lake completely dried up. As a consequence, all of the fine, salt-encrusted particles at the lake bottom were exposed to the wind and many were picked up, turning strong winds turned into dust storms.

In the 1970s, the United States passed the “Clean Air Act”, placing limits on air pollution, including particulate air pollution like that generated by an artificially dried lake bed. The Clean Air Act actually forced Los Angeles to act.

Starting in the late 1990s, small amounts of water were diverted back to Owens Lake, keeping the flat lakebed partially flooded and shutting down the dust storms. The presence of thin, salty layers of water have allowed algae to grow, turning the evaporation ponds red in many of the photos.

The environmental disaster that was Owens Lake has been partially contained, but the mountain lake that used to sit on this site will never come back. Something like Owens Lake may be the end result of many drying lakes around the world; kept just wet enough to prevent dust from blowing, but without enough water to create a vibrant ecosystem.

-JBB

Image credits: https://flic.kr/p/992v8K http://bit.ly/1B1vgxX http://bit.ly/1zF06RD

Read more: http://www.epa.gov/region9/air/owens/history.html http://geochange.er.usgs.gov/sw/impacts/geology/owens/ http://www.desertusa.com/desert-california/owenslake.html http://www.owenslakeproject.com/ Live webcam: http://www.gbuapcd.org/dustcam.htm

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Fossil bees!

This pair of images shows, on top, a modern-day leafcutter bee from the species Megachile rotundata and a very cool fossil find from the LaBrea Tar Pits. The bees come from a pair of full nests exhumed from a part of the tar pits; the same location has produced bones from animals 23,000 to 40,000 years old, and carbon-14 dating of the material in the nests gives the same age, so these bees are about that old. Many interesting specimens are preserved in the nests and have been found by scientists exhuming material from the tar pits, including the leafy walls of the nests themselves, adults, and pupae like this one.

The bees are from species that are widespread in the United States, but the presence of these bees at this site actually helps constrain how their distributions have changed during the big climate shifts that happened since the nests were made. The bees today have expanded ranges at higher elevations than is suggested by these fossil finds, indicating that as the climate of the area warmed, the bees moved uphill to follow similar temperature levels.

-JBB

Image credit:

Image credit: PLOS One (Open access journal): http://www.plosone.org/article/info%3Adoi/10.1371/journal.pone.0094724

Skyscrapers of Los Angeles swallowed by the Pacific Ocean Marine Layer

tdangphotoTime lapse of the something I have been waiting to capture for a long time. <be sure to Turn on the sound>