Sunday, 31 May 2015

Planet Earth - When humans finally dominated Earth .... perhaps the year 1610?

Researchers suggest the geological epoch known as the Anthropocene probably began around the year 1610.

Scientists say that humans have become a 'geological power'.

They suggest that humans have produced a new geological epoch.

The key markers for 1610 were -

1 - an unusual drop in atmospheric carbon dioxide, and 

2 - the irreversible exchange of species between the New and Old Worlds, according to new research published in Nature.

The drop in CO2 was caused by colonisation of the "New World"....North and South America.

That event led to the deaths of about 50 million indigenous people, most within a few decades of the 16th century, due to smallpox. 

Yes, 50 million people .....

The sudden collapse of farming across the Americas, and the re-growth of Latin American forests, removed enough carbon dioxide from the atmosphere to produce a drop in CO2.

Humanity had become a force of nature.

Saturday, 30 May 2015

Planet Earth - El Nino

El Niño is an oscillation of the ocean-atmosphere system in the tropical Pacific, and has important consequences for weather around the world.

El Niño happens every three to seven years.

“El Niño” is Spanish for “The Christ Child”.

Peruvian fishermen named the event many years ago.
They noticed that every few years around Christmas, virtually no fish could be found in the unusually warm waters. 
El Niño is marked by unusually warm ocean temperatures in the Equatorial Pacific.

The opposite conditions are called La Nina, characterized by unusually cold ocean temperatures in the Equatorial Pacific. 

El Nino clearly affects global temperatures.

Information about El Nino is provided in bulletins produced by the US National Weather Service and the Australian Bureau of Meteorology.

Friday, 29 May 2015

Planet Earth - The End-Permian Mass Extinction

Five major mass extinction events are recorded in the rock record of the last 600 million years.
The biggest extinction was at the end of the Permian, around 252 million years ago.

It is called the End-Permian mass extinction.

Only about 8% of species survived to live on in the Triassic Period.
The event played out over 60,000 years.
Acidification of the oceans lasted for about 10,000 years.
Two separate pulses of CO2 into the atmosphere - a "one-two punch" - may have been involved in the die-off, according to new research.
CO2 was released by massive volcanism from the Siberian Traps, now represented as a large region of volcanic rock. 

The research team, led by Dr Matthew Clarkson from the University of Edinburgh, examined rocks in the United Arab Emirates. 
Siberian Traps
The rocks, which were on the ocean floor at the time, preserve a detailed record of changing oceanic conditions. 

The carbon was released at a similar rate to modern emissions. 
Matthew Clarkson image
Dr Clarkson says "Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now.
"This is a worrying finding, considering that we can already see an increase in ocean acidity today that is the result of human carbon emissions."

Thursday, 28 May 2015

Planet Earth - Ammonites

Ammonites are an extinct group of sea creatures.

They were cephalopod molluscs, related to squid and octopus.

They are found as fossils, formed when the shells of the animals became buried in sediment which later solidified into rock.

The oldest ammonite fossils are found in Jurassic rocks, from around 200 million years ago. 

They became extinct at the end of the Cretaceous around 65 million years ago.

Ammonites had shells made of chambers. The air in the chambers helped them to swim.

There are hundreds of types of ammonites, with different shapes.

Here are just a few examples.

Wednesday, 27 May 2015

Planet Earth - The Discovery of the Dinosaurs

In 1822, Mary Mantell was looking at rocks alongside a country lane in Sussex, England.

She noticed something odd in the rocks.

Two of the first Iguanodon teeth ever found

Her husband, Doctor Gideon Mantell, was visiting a patient nearby, and they took the rocks home.

Gideon and Mary Mantell

The teeth Mary Mantell had found were like those of an iguana, a well-known lizard, but much larger.

Doctor Mantell chose the name Iguanodon for the animal which had once owned the teeth.

Over the next twenty years various other ancient bones and teeth were linked to giant land-living reptiles.

In 1842 Richard Owen, superintendent of the Natural History Museum in London, called these animals dinosaurs.

At first, not many full skeletons were found, so rebuilding dinosaurs was difficult.

Richard Owen thought Iguanodon looked like this model, made in the 1850s.

Lots of fossils have been found since, which makes it easier to see a better idea of this amazing animal.

Tuesday, 26 May 2015

Planet Earth - Greenland

The invention of the name Greenland may mark the start of the advertising industry.

One story tells how Erik the Red, the Icelandic Viking who wanted to get people to join his planned settlement, called it Greenland because a pleasant name would attract more settlers.

The ice sheet on Greenland covers most of this huge island.

Each summer the ice surface melts in places, but the area where melt happens is increasing over time.

Greenland is losing ice, and the mass of ice lost is measured by satellites called Grace.

Updates about Greenland's ice sheet are regularly posted by the National Snow and Ice Data Center.

Monday, 25 May 2015

Planet Earth - Icthyosaurs

Life restoration of Ichthyosaurus anningae. Image credit: James McKay.
Life restoration of Ichthyosaurus anningae. Image credit: James McKay.

A remarkable discovery in the fossil collection of the Doncaster Museum and Art Gallery has led to the naming of a new species.  

Ichthyosaurus anningae

A new species of Ichthyosaurus.

Picture Credit: Dean Lomax and Judy Massare

The name honours Dorset fossil collector Mary Anning.

It was Mary, along with her brother Joseph, who found the first Ichthyosaurus fossils to be scientifically studied in 1811.

Until now, no species of Ichthyosaurus has been given her name, so this is long overdue.

Dean Lomax, Honorary Scientist at The University of Manchester, examined the specimen in 2008.  

Sunday, 24 May 2015

Planet Earth - Tropical storms

Hurricanes, cyclones, and typhoons are all the same weather phenomenon; we just use different names for these tropical storms in different places. 

In the Atlantic and Northeast Pacific, the term “hurricane” is used, in the Northwest Pacific it is a “typhoon”, and “cyclones” occur in the South Pacific and Indian Ocean.

Tropical storms can’t form outside the tropics - water temperatures are too cold.

Sea surface temperature must be at least 27°C, and this temperature is actually required to a depth of at least 50 m

The warm tropical atmosphere heats up the water at the ocean surface and begins to evaporate it. 

The trapped water vapour in the air rises up through the atmosphere. 

When the rising air cools, and the water vapour condenses into liquid water, the heat is released back into the atmosphere.

The warm air rushes upward, because it has a lower density than its surroundings. 

This then draws air up from below, and speeds up the rising air near the surface. 

Surface air around the growing disturbance rushes in to replace it. 

A satellite image from the National Oceanographic and Atmospheric Administration shows Hurricane Katrina bearing down on the Gulf Coast on Aug. 28, 2005.

As this cycle continues, more warm, moist air is drawn into the developing storm, and more heat is transferred from the surface of the ocean to the atmosphere. 

This continuing heat exchange creates a wind pattern that spirals around a relatively calm centre, or eye, like water swirling down a drain.

Saturday, 23 May 2015

Planet Earth - Intrusive & extrusive igneous rocks

There is a famous rock face just below Salisbury Crags in Holyrood Park, Edinburgh.

The rock face tells us about the hot volcanic past in Scotland.

It's called "Hutton's Section" after James Hutton who first noticed it.

The pale layered rock is broken and tilted by the reddish-brown massive rock.

Hutton realised the reddish-brown rock must have been molten magma, pushing with force into the older sedimentary rocks.

This is an example of an intrusion.

The reddish-brown rock is a variety of igneous rock called dolerite.

Edinburgh sits on an ancient volcanic centre.   

The volcanic activity happened in the Carboniferous Period.

In this view, Salisbury Crags palisade stands over the city - it is a sill.

On the right is Arthur's Seat, made of four eroded central volcanic vents.

This diagram explains how some volcanic landforms are made.

A sill is one type of igneous intrusion.

Fingal's Cave is on Staffa, an island near Scotland.

The island, like many of the Inner Hebrides, is made of volcanic rock.

In this case the igneous rocks are called 'extrusive', because they formed on the surface.

The vertical lines seen in the photograph were formed when hot lava cooled.

The shrinking basalt lava produced a columnar pattern.

These volcanic rocks date from around 50 to 60 million years ago.

At that time, the North Atlantic was starting to form, with Europe beginning to split from North America.

This diagram shows how volcanoes developed between Europe and North America 60 million years ago, as magma from deep in the Earth moved upwards and was erupted at the surface. Volcanism has continued ever since along a structure called the Mid-Atlantic Ridge, creating new ocean floor and pushing the continents steadily apart at a rate of a few millimetres a year. In Iceland, this steady volcanism has interacted with a hot mantle plume to create the volcanic island we see today. (Image: © Elizabeth Pickett

This diagram shows how volcanoes began to separate Europe and North America 60 million years ago.

Magma from deep in the Earth moved upwards and was erupted at the surface. 

Volcanism has continued ever since along a structure called the Mid-Atlantic Ridge.

It created the Atlantic ocean floor and is still pushing the continents steadily apart at a rate of around 2.5 centimetres a year. 

In Iceland, this steady volcanism has interacted with a hot mantle plume to create the volcanic island we see today. (Image: © Elizabeth Pickett)

Friday, 22 May 2015

Planet Earth - Fossil footprints

Footprints of many kinds of creatures have survived as fossils in rocks.

This can be because they were quickly covered by volcanic ash, or layers of fine clay, preserving the details.

These footprints were most likely made by Australopithecus afarensis, an early human whose fossils were found in the same sediment layer.

They were found at Laetoli in Tanzania.

Looking at much older rocks, footprints of dinosaurs can be used to find out all sorts of things about their lives.

Thursday, 21 May 2015

Planet Earth - The Polar Regions

The Earth's poles are warming faster than the rest of the planet.

One reason is that energy is carried to the poles by large weather systems.

The Arctic includes an ocean covered by sea ice.

Arctic sea ice melts in Summer and then refreezes in Winter.

The area of Arctic sea ice is largest in March each year, and at its lowest each September.
It is reducing over time - the graph comes from the US National Snow and Ice Data Center.

ice extent trend graph
Research suggests the remarkable decline of  Arctic sea ice over the last century is far beyond anything seen for a long time. 

The Antarctic is a continent covered by ice, unlike the ocean in the Arctic.

The sea ice surrounding Antarctica melts almost to the coast each summer.

The winter sea ice has increased by around 1 % over the last few decades.

This is due to complex processes.

It is linked to melting of the land ice on Antarctica…..

Here is an outline of what is happening in the seas around Antarctica:

Seawater does not freeze until around minus 2 degrees C because it is salty.

This effect of salt, of course, is used to help defrost roads.

The meltwater off Antarctica’s ice sheets is freshwater.

Freshwater has a low density, so it forms a layer on top of the sea.

Freshwater freezes (of course) at zero degrees C.

The top layer of fresh water freezes more easily than  normal seawater.

Also wind-chill helps to freeze that top layer.

So there is more winter sea ice now.

For a useful comparison of Antarctic and Arctic sea ice follow this link……

Wednesday, 20 May 2015

Planet Earth - Iceland, a land of ice & volcanoes

Iceland lies on the Mid-Atlantic Ridge, which is why it has volcanic activity.

Iceland also has ice caps and glaciers.

Iceland is one of the fastest-warming places on the planet – as much as four times the Northern Hemisphere average. 
The glaciers that cover more than 10% of the island are losing an average of 11 billion tonnes of ice a year. 
              Iceland glacial meltwater - photo Tom Harding
The water melting from Iceland's glaciers would fill 50 of the world's largest trucks every minute for the entire year.

Parts of Iceland are rising as the ice caps melt, reducing the weight on the Earth's crust.

The thinning of the ice caps reduces the pressure on the rocks.

Geologists know reduced pressure from above makes volcanoes erupt more easily.

Lower pressure allows volcanic gases to expand, and mantle rocks melt more easily at lower pressure as well.
This means more magma can rise into the volcanic systems.
Iceland's volcanoes may get more active as a result.

Tuesday, 19 May 2015

Planet Earth - Ancient desert sandstones

Some sandstones have very obvious sweeping curved patterns within their layers.

This sandstone dates from the Permian period, and is in south Devon.

Cross-bedded Permian Sandstone

This pattern is called cross-bedding.

It is formed when loose sand is moved, sometimes by water and sometimes by wind.

This larger sized cross-bedding is more often linked to wind movement, but to be sure geologists look closely at the sand grains.

The grains are mostly rounded off, not sharp, which shows they were blown by the wind.

This suggests that the sandstone was produced in a desert.

The cross-bedding forms as sand flows down the front of sand dunes.

Another well-known cross-bedded sandstone is the Coconino Sandstone, seen in the Grand Canyon.

It is another Permian rock, formed in a desert.

Monday, 18 May 2015

Planet Earth - Caves, Stalactites and Stalagmites

Speleothems are cave features formed by  minerals. 

The word speleothem comes from the Greek words spelaion meaning "cave" and thema meaning "deposit". 

The most well-known speleothems are stalactites and stalagmites

Stalactites grow down from the cave ceiling.

Stalagmites grow up from the cave floor. 

It’s easy to remember which is which: 

Stalactites have a "T" for top and stalagmites have a "G" for ground.

Caves, stalactites and stalagmites are caused by chemical reactions.

Sunday, 17 May 2015

Planet Earth - Geothermal Heat in Antarctica

There have been very inaccurate stories on various websites claiming ......

"Volcanoes are the main reason for ice melting in Antarctica."

This is not the case.

The story is mainly a misreading of research on the Thwaites glacier.
This is the actual paper about this research......
So what actually is happening? 

The Thwaites Glacier is behaving more like a warm-based glacier.

The geothermal heat from under the Thwaites glacier is small compared to the overall warming happening around Antarctica.
The Thwaites Glacier is one of a number of glaciers in that part of Antarctica.
“It is true that there are active volcanoes in West Antarctica, and so there may have been some local changes, but in most cases, at most times, volcanoes are not erupting under the ice,” Richard Alley, a geologist at Penn State University, told VICE News. 

“This paper doesn’t tell you anything about why the ice is now thinning.”

Eric Rignot, an earth science professor at University of California Irvine and a principal scientist at NASA, said geothermal heating causes a few millimetres of glacial melting each year.

Rising sea temperatures can melt up to 100 metres of a glacier each year, he said.A photo of Thwaites glacier in West Antarctica taken by NASA Operation IceBridge. A new study finds a rapidly melting section of the West Antarctic Ice Sheet appears to be in an irreversible state of decline, with nothing to stop the glaciers in this area from melting into the sea. Credit: NASA     A NASA photo of the Thwaites Glacier at the point it meets the ocean.

The heat flow out of the crust is highest at the spreading ocean ridges.