Where in the Earth would you be the heaviest? Standing on the surface of Earth, or in orbit around the Earth, to a first approximation the gravity of the planet is no different whether the planet has a lot of mass right at the center or has mass evenly distributed throughout, or has all its mass right at the surface. However, if you moved down through the planet, the gravity will change. If all Earth’s mass was at the center, you’d find that gravity increased as you approached the center, then dropped right as you reached it. If most of Earth’s mass was near the surface, you’d find gravity gradually decreased as you moved towards the center.

Sandstone Formations

Natural sandstone arches are a wonder to see, but how do they form? A 2014 study has provided a plausible explanation for how these and other formations are created, even though they may seem to defy gravity.

Creation of sandstone formations has long been attributed to erosion and weathering, but it turns out the rocks themselves, with help from gravity, deserve credit as well. When erosive forces act on a rock, they have the biggest impact wherever there is weakness in the structure, such as a fracture in the stone. Water, wind, and frost can easily remove pieces of the sandstone thereby undercutting it.

As parts of the sandstone are eroded, the remaining intact rock is subjected to greater downward forces from supporting the weight of everything above it. Instead of collapsing, the added pressure (pressure = force divided by area) causes the sand grains within to lock together, increasing stability. Eventually a critical pressure is reached where the sand grains are locked so tightly that they resist erosion, while areas under low stress will continue to erode away revealing an arch or other formation. The specific shape depends greatly on where any weakness in the sandstone where erosion may have been most effective.

We recently posted a great example of how strong sandstone rocks can be under pressure:http://on.fb.me/1Mwv7dI

Photo Credit: Jim Karczewski, U.S. National Park Service

References: http://bit.ly/WrmlsQ http://bit.ly/1qyw4uP

Common Geologist Convo #1

Weight

This space shuttle image looks southeast towards the Persian Gulf and the huge Zagros Mountains in southern Iran. The combination of this mountain range and the intruding waters is not a coincidence.

The Persian Gulf actually exists today because of the weight of the mountains. Building a mountain range like the Zagros requires piling up huge amounts of rock on the top of the Earth’s surface. The Earth’s mantle beneath the mountains is soft, a state we call “plastic”, and able to flow over geologic time, while the more rigid crust on top is able to bend.

Imagine taking a giant mass and just dropping it on top of a mattress. The mattress won’t just be pushed down where the weight sits; the whole area around the weight will bend down in response to the weight.

The Persian Gulf is the end result of this effect. The huge weight of the Zagros Mountains has deformed the Earth’s crust in the entire area, pushing the planet’s surface down so far that the land has moved below sea level and the ocean has flowed in.

-JBB

Image credit: Image Science & Analysis Laboratory, NASA Johnson Space Center http://oceanleadership.org/scientists-use-ocean-drilling-data-to-connect-seawater-chemistry-with-climate-change-and-evolution/

Read about foreland basins: http://www.hiddenjourneys.co.uk/Cairo-Doha/Persian%20Gulf/Highest/hjp.PGF.WIKI.008.aspx?mode=image

Major impacts on dolphins from Deepwater Horizon oil spill

It’s been several years since the Deepwater Horizon oil rig exploded in the Gulf of Mexico, leading to one of the largest oil spills in recorded history. That means we’re now getting good scientific studies of how the ecosystems in the gulf reacted to and recovered from the disaster.

A study has just been published in the journal Environmental Science and Technology looking at the health of dolphins in the Gulf after the spill and their results are disconcerting.

A team led by NOAA scientist Lori Schwacke visited Batavia Bay off the coast of Louisiana in 2011, over a year after the start of the oil spill, and investigated the health of local dolphins. Their results weren’t positive, to say the least.

Of that group, 48% were unhealthy. In the group exposed to the oil, they found a variety of issues, including hypoadrenocorticism (consistent with adrenal exposure to toxic chemicals), lung issues at 5 times the rate of the normal population, and large numbers that were underweight. Many of the dolphins with breathing issues also had growths on or within their lungs.

Of this group, they estimated that just under 20% would be unlikely to survive, and 30% were marginal cases.

By comparing this population to dolphins in Florida, unaffected by the spill, the scientists make a strong case that the problems in the Batavia Bay dolphins are directly related to the spill. Populations in the area not exposed to the oil don’t have similar problems, and the issues are the exact problems that would be expected from exposure to oil.

Most of the oil released by the Deepwater Horizon was consumed rapidly by microbes in the Gulf. However, it’s clear from this study that the spill caused damage to the ecosystem that was still visible in the dolphins over a year later.

-JBB

Image credit: NOAA http://blogs.nature.com/news/2011/03/counting_corpses_underestimate.html

Press report: http://www.nola.com/environment/index.ssf/2013/12/half_of_bottlenose_dolphins_of.html Original paper: http://pubs.acs.org/doi/full/10.1021/es403610f

Driving out onto Lake Baikal, Russia (check out the cracks in the ice that have healed enough to support a car)

Snowy Shoreline

Each of the lines standing out due to the snow settling into low spaces is a shoreline. This photo was taken on Southampton Island, which sits in the outlet of Canada’s Hudson Bay. 20,000 years ago there was about 4-5 kilometers of ice sitting atop of this site – that height of ice would dwarf the largest skyscraper ever built by humans. The huge weight of that ice caused the Earth’s mantle to actually flow away, creating a deep depression in the heart of what is now Canada.

Once that ice melted, the weight was removed and the mantle deep below began flowing back in, pushing the landscape upward. As the land has popped up, the waters of Hudson Bay have cut one shoreline after another into the land. Those shorelines are marked in this photo by the high and low ground, well illustrated by the snow. The frozen, flat area at the left is the open water.

-JBB

Image credit: Mike Beauregard https://flic.kr/p/n4CLKN

The Paleontology of Pound Stones Dairymaids of 18th century England may have been some of the best unintentional paleontologists. In a time before standardized measurements, these dairymaids often used “pound stones” to weigh out butter and cream. These pound stones, commonly found in the fields of Oxfordshire, were particularly useful because all were uniform in shape, size and weight. Dairymaids recognized the practical value of a pound stone, but it would be a few years before anyone realized their scientific importance. What were these unique rocks that aided rural dairy farmers? Pound stones were circular, often flat on the bottom, had 5-fold symmetry, and closely resembled a familiar living creature…the sea urchin. Pound stones, or Chedworth buns as they were sometimes called, turned out to be fossilized sea urchins. As scientific discovery continued to progress, geologists realized that these useful pound stones were not only weights, but signs of ancient oceans that once covered England. This particular species of urchin, Clypeus Ploti, is found in Jurassic limestones and is still a valuable chunk of history for fossil collectors today. -CM Photo courtesy of Flickr user Rockman of Zymurgy http://bit.ly/1A6K2FA

Weight This space shuttle image looks southeast towards the Persian Gulf and the huge Zagros Mountains in southern Iran. The combination of this mountain range and the intruding waters is not a coincidence. The Persian Gulf actually exists today because of the weight of the mountains. Building a mountain range like the Zagros requires piling up huge amounts of rock on the top of the Earth’s surface. The Earth’s mantle beneath the mountains is soft, a state we call “plastic”, and able to flow over geologic time, while the more rigid crust on top is able to bend. Imagine taking a giant mass and just dropping it on top of a mattress. The mattress won’t just be pushed down where the weight sits; the whole area around the weight will bend down in response to the weight. The Persian Gulf is the end result of this effect. The huge weight of the Zagros Mountains has deformed the Earth’s crust in the entire area, pushing the planet’s surface down so far that the land has moved below sea level and the ocean has flowed in. -JBB Image credit: Image Science & Analysis Laboratory, NASA Johnson Space Center http://oceanleadership.org/scientists-use-ocean-drilling-data-to-connect-seawater-chemistry-with-climate-change-and-evolution/ Read about foreland basins: http://www.hiddenjourneys.co.uk/Cairo-Doha/Persian%20Gulf/Highest/hjp.PGF.WIKI.008.aspx?mode=image