It has been a while since I checked in with the NASA webpage http://earthobservatory.nasa.gov/. Here are some images from that page.
This week marks the 100th anniversary of the National Park Service. We are celebrating this milestone with a gallery of images. The photo above shows the northern tip of Wisconsin, where the land reaches into the
cold deep of Lake Superior. Apostle Islands National Lakeshore includes 21 islands and a strip of
mainland at the top of Wisconsin. Management of the islands by the
National Park Service (NPS) began in September 1970. More lighthouses
stand within this parkland than in any other NPS property.
Author F. Ross Holland wrote in
Great American Lighthouses:
“Within the boundaries of Apostle Islands National Lakeshore is the
largest and finest single collection of lighthouses in the country.” The
oldest, Old Michigan Island Lighthouse, was placed into service in 1857
as an aid to ships crossing Lake Superior. Today there are five
lighthouses and four light towers spread across Sand Island, Raspberry
Island, Devil's Island, Outer Island, Michigan Island, and Long Island.
Besides the lighthouses, the area is famous for its shoreline cliffs,
sea caves, and other rock formations. Red sandstone was deposited a
billion years ago during the late Pre-Cambrian Era, and it has been
carved and sculpted for millions of years by rising and falling water
levels and by waves of advancing and retreating glaciers. Glaciers have
also dropped an abundance of till and flour here. Wind and water have
ground the rock into sands that aggregate in spits, sandbars, mounds
(tombolos), and some of the lake’s most pristine beaches. In some
places, freshwater rock pools provide unusual habitat for amphibious life and insects.
The Apostle Islands, so named by Jesuit missionaries during colonial
days, have seen their share of farming and logging over the past few
centuries. But today, most of the islands have been reforested
naturally, and some stands of old-growth forest remain.
Ancient clams, 35-million-year-old rhinoceros-like creatures, and a
thick coat of volcanic ash—all of these are baked into the layer cake of
stone at Badlands National Park. Over epochs, deposition and erosion
have carved sharp spires and deep canyons out of this South Dakota
landscape. Visitors to this park can wander alongside, under, and
between millions of years of geologic history.
The Badlands have long been a choice destination for fossil hunters, as the stone here dates back roughly 75 million years to when the Great Plains were covered by a shallow, inland sea. As the water level dropped and the sea floor became land, the Pierre Shale
(the bottom most rock layer of the Badlands) crumbled into soil and
created the Yellow Mounds Formation, so called because of its
mustard-like color. By 34 to 37 million years ago, when subtropical
forests covered the land, river flood plains created the Chadron
Formation, Eocene-era mud rocks under North Dakota, South Dakota, and
Nebraska.
Then, 30 to 34 million years ago, the climate began to dry and cool. Savannah replaced forests, and oreodonts (sheep-like mammals) walked these lands. This era gave rise to the Brule Formation,
a gray layer of stream and floodplain deposits. Later in the Oligocene
Epoch, about 28 to 30 million years ago, a dense layer of volcanic ash
from episodic eruptions in the Great Basin covered the landscape. It was
this ash, along with sandstones, stream channel sand, and floodplain
mud that created the Sharps Formation, which constitutes the uppermost
layer of the Badlands today.
Fast forward millions of years, and the Badlands have a different
sort of history. One hundred and fifty years ago, the Great Sioux Nation
(including the Oglala Lakota) dominated the northern prairie. The
valleys of the Badlands provided the tribes with shelter, fresh water,
and game to hunt. But by the late 1800s, homesteaders arrived in South
Dakota. Prairie land was converted for farming and ranching purposes,
and the Sioux were forced out their former territory.
The Badlands National Monument was created in 1939, and the area was
soon cleared of residents. During World War II, the U.S. Air Force used
the land as a practice gunnery range.
Badlands was designated a national park in 1978, and the Park Service
included surrounding grasslands and the boundaries grew to encompass
roughly 610 kilometers (380 miles).
“The preservation of this relatively small exhibit of native grass is
an important responsibility in itself, since no comparable section of
the Great Plains has been set apart to be preserved in its natural
condition,” the National Park Service declared in a 1952 statement. Grazing there was phased out over several years beginning in 1961.
Today, the park is home to bison, bighorn sheep, prairie dogs, and
black-footed ferrets. Visitors can hike along trails or drive, taking in
the view from South Dakota’s Highway 240.
Red-hot streams of molten rock sliced
across the hard, black landscape. The lava hissed violently as it
dropped into the Pacific near Hawaii’s Volcanoes National Park. Nearby passengers aboard a small boat could feel its 2,000-degree heat warming their faces.
In the following days, a small new delta
formed, jutting into the sea southeast of the Pu’u O’o volcanic cone.
Hawaii had grown again, gaining a few more feet in a process that began
tens of millions of years ago and thousands of miles below Earth’s
surface.
The story of the Hawaiian Islands begins at a hot spot,
a point where magma from Earth’s mantle penetrates the crust. As the
Pacific tectonic plate has moved over it, this stationary jet of magma
has acted like a laser cutter, punching holes in the seafloor and
ejecting molten rock to create an archipelago. Over the years, these
islands have grown and their contours have changed. During the frequent
eruptions of the various volcanoes, lava has devoured trees and structures, but also built new land. Winds and ocean waves have carved the edges, creating cliffs.
This turbulent landscape has been home to people for centuries.
Hawaii’s first settlers likely came from the Marquesas Islands around
500 C.E. A second migration, from Tahiti, began sometime between 1200
and 1400 C.E.
In 1823, William Ellis, an English missionary, became one of the
first Europeans to feel the hot breath of Kilauea volcano. After an
hours-long climb—through a tangle of sopping rain forest and then across a
rocky, moon-like landscape quenched by acid rain from the volcano’s
sulphuric fumes—Ellis reached the edge of the crater. He stood rooted to
the spot. Below, a “cauldron of lava” boiled. Dense columns of smoke
and vapor rose from the abyss. Ellis waited without speaking. He
listened to “the constant roaring of the vast furnaces below.”
For hundreds of years, visitors have come to the park on Hawaii’s
largest island to peer down into the abyss. Volcanoes National Park was
established on August 1, 1916. In 1987, the park became a World Heritage Site. 2016 has been marked by centennial celebrations.
Volcanoes National Park includes the Earth's largest volcano, Mauna
Loa. It stands 13,677 feet (more than 4,000 meters) above sea level,
according to the National Park Foundation.
But what visitors see merely represents the tip of the mountain. If you
measure from the sea floor, Mauna Loa’s summit stretches roughly 56,000
feet (17,000 meters) above its base. That’s more than 27,000 feet
(8,230 meters) higher than Mount Everest.
The Mauna Loa Observatory,
a small white orb at the end of a long thread (Mauna Loa Observatory
Road), has been measuring carbon dioxide levels from near the volcano’s
summit since the 1950s. Dried lava flows appear like deep, dark
scratches in the surrounding hills.
Neighboring Kilauea is the world’s most active volcano, and one of the best-studied on the planet. Easy road access has led some to call it a “drive-up” volcano. But visitors ignore warning signs at their own peril. Park rangers
caution that the ground may be unstable underfoot, as a crust of
hardened lava may sit atop a hot, molten river or a hollow air tunnel.
Acidic smoke, laden with lung-irritating particles, billows out of
craters.
The Ojibwa tribe has a heart-rending legend that explains how the dunes of Sleeping Bear Dunes National Lakeshore and two nearby islands in Lake Michigan formed.
The legend says that long ago, a mother bear and two cubs were driven
into the lake by the encroachment of fires on land. After hours of
swimming, the mother bear reached the far shore of the lake. But when
she turned around to check on the progress of her cubs, she saw nothing.
Both of them had slipped beneath the lake surface and disappeared. The
mother bear spent days staring out across the lake in the hopes they
would eventually swim ashore. But after weeks of waiting, the
heartbroken mother bear laid down to sleep on a bluff overlooking the
lake and never woke up. In recognition of her suffering, the Ojibwa say a
powerful spirit covered her with sand and made her two cubs rise above
the water as North and South Manitou island.
Geologists have a different way of explaining the formation of the
dunes and the two islands. The geological story begins with ice. During
the last Ice Age,
glaciers spread southward from Canada, burying the area under thick
sheets of ice. As these sheets of ice slid southward, they ground parts
of the underlying bedrock into sand under their tremendous weight. When
the ice eventually retreated about 12,000 years ago, it left behind
large piles of sand and rock debris called moraines, creating the hilly terrain visible along the lakeshore today. Sand deposited by glaciers is the main ingredient for the “perched dunes”
located on bluffs relatively high above the water level. Meanwhile, the
combined pounding from winds, waves, and lake ice also built dunes at
lower elevations along the shoreline from beach sand.
The images above show Sleeping Bear Dunes National Lakeshore, which
spans 56 kilometers (35 miles) along the eastern shore of Lake Michigan.
The orange lines mark the boundary of the national lakeshore. In the
lower image, notice the tan sand dunes on a plateau between Glen Lake
and Lake Michigan.
CITES:
ASA Earth Observatory image by Jesse Allen, using Landsat data from the U.S. Geological Survey. Caption by Mike Carlowicz.
NASA Earth Observatory image by Joshua Stevens, using Landsat data from the U.S. Geological Survey and ASTER GDEM data from NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team. Photograph courtesy of the National Park Service. Caption by Pola Lem.
NASA Earth Observatory images by Jesse Allen, using Landsat data from the U.S. Geological Survey and Space Shuttle photograph STS61A-50-57
which was acquired on November 1, 1985, with a Hasselblad medium format
camera with a 250 millimeter lens, and is provided by the ISS Crew
Earth Observations Facility and the Earth Science and Remote Sensing
Unit, Johnson Space Center. Caption by Pola Lem.
NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey. Caption by Adam Voiland.
