Magnetic Anomalies in the earth’s field

Many are familiar with the idea of magnetic poles flipping every 200,000 years or more, (if not have a look at my previous blog). Evidence for this was found in the 1960’s when scans by aircraft looking for submarines showed some strange anomalies in the strength of the magnetic field at different locations. It was later realised that basalt, a volcanic rock containing magnetite, fixes the current magnetic orientation of the earth’s magnetic field as it cools down. The younger the rock the closer it aligns to the current magnetic north, older basalt rock shows evidence of previous magnetic fields and that the magnetic poles flip so north becomes south. This can be seen when taking magnetic readings of the basalt rock emanating from the mid Atlantic ridge where the tectonic plates are being forced apart as volcanic rock pushes up from the upper mantle. The process of millions of years of new rock being pushed out, like the rings of a cut tree, show lines indicating different polarities of earths history. The image below shows the magnetic striping of the sea bed of the mid Atlantic ridge, the darker tone, the closer it is to out current North / South orientation, the lighter tone shows the opposite polarity. In effect the sea bed is like a tape recording of the earths magnetic past, as the theory was accepted a new area of plate tectonics was born called Magnetostratigraphy.

different magnetic fields emanating from the mid Atlantic ridge

Further anomaly’s have since been mapped by NOAA, this image shows more subtle variations in the earths magnetic field strength.

the world digital magnetic anomaly map

web references:

Without bacteria we wouldn’t have skyscrapers…

Periodic table Number : 26    /    known as element  “Fe” (from latin Ferrum)

Iron is the most common element on earth by mass, it’s found in rocks and living things.  It’s in our blood which is why its red in colour due the reaction with oxygen when transferred from our lungs into the haemoglobin.  But how did it get there in the first place?  To understand this we need to take a big step back in time, 1.8 billion years ago, when atoms of iron were floating around in the oceans.  Bacteria capable of photosynthesis releasing oxygen into the sea enabled iron to be converted into hematite and magnetite minerals which sank to the sea floor.  This was fundamental to the geological process in forming iron deposits which were later covered by other minerals and compressed into rock over millions of years.

iron ore mine in Australia

Iron ore was first used in the near east and spread around the Mediterranean in all directions expanding populations as a result of more efficient tools and the ‘iron age’ began.   The end of the bronze age around 1200BC was heralded by the development of iron smelting (heating iron ore with coal) which in turn lead to the birth to the industrial revolution in Northern Europe changing societies rapidly with mass production methods.

ancient iron smelting technique in Rwanda

Skyscrapers rely on steel (99% iron 1% carbon) to give the structure enough strength to build as high as the Burj Khalifa in Dubai at 828 meters, all thanks to bacteria

Today we can see chemotrophic bacteria which get their energy by oxidising molecules of iron and therefore thrive in areas rich in iron deposits so the bacterial cycle continues. .  When you see orange coloured stream beds you are seeing the specialised iron oxidising bacteria at work.

Humans need iron or we become anaemic (tired and lacking vitality) and we get this by eating food containing iron.  Humans are 10%  bacteria (by mass) and those bacteria too need iron and they have specialised ways of harvesting the iron they need from their human host. “Iron is the single most important micronutrient bacteria need to survive,” (Doyle, 2008) and without bacteria humans can’t survive.  This is one of the many symbiotic relationships animals and humans have with bacteria.

bacteria that feed on iron


Doyle, 2008: Journal of Bacteriology (volume 190, issue 16) published by the American Society for Microbiology.

Iron-Oxidizing Bacteria: