Rocks and soils on your farm – more about basalt!

Recent basalt lava flows - amazing shapes!

Recent basalt lava flows – amazing shapes!

Nothing is more amazing than watching hot liquid rock (lava) flow over the ground creating amazing shapes and making an amazing sound.  I am been fortunate to see this wonder a couple of times…and its lure to see it again is so strong that I may end up living in Hawaii one day.  If that happens, I will be farming on basalt!

Me - standing on basalt columns formed from the cooling of a thick lava flow in Iceland.

Me – standing on basalt columns formed from the cooling of a thick lava flow in Iceland.

What is basalt?
Basalt is a very dark, find grained volcanic igneous rock that has formed form the cooling of molten rock.  Basalt is found around the globe as it makes up the ocean floors and some huge tracts of land on continents where there has been massive eruptions in the past – such as the Colombia River region in the NW of the USA , Siberian Traps in Russia.   In other locations, small basalt outcrops occur where once lava flowed from small volcanic vents that may have been active for a very short time – and all the remnant volcanic features (cones etc) have completely vanished.

What is gabbro?
Gabbro is the course grained equivalent of basalt.  Unlike basalt that cooled quickly from lava flowing n the surface, gabbro cooled slowly deep inside the Earth forming larger crystals all locked together.

Volcanic stuff

A volcano is a place where molten rock flows from inside the earth and cools on the surface….and I am sure everyone has a picture of a volcano in their minds.  Volcanoes vary immensely in their size and shape dependent on  the type of materials that erupt.  Basalt volcanoes erupt mostly thin flows of black lava – but they can also produce cinder (frozen droplets) and ash (fine particles).  Cinder is loose material that can produce a great growing medium if other nutrients are added and is used in some places as the basic ‘soil’ in hydroponic systems.   That same cinder when it is larger in size is used as ‘bbq rocks’ in some gas grills.

Basalt soils
Basalt contains minerals that are rich in iron and magnesium – such as olivine and pyroxene – along with sodium and calcium rich feldspars.  All these minerals weather to form iron rich clays that are often rusty-red in color.

Olivine crystals in basalt

Olivine crystals in basalt

So the soils on basalt are normally iron rich, clay based soils which can be very fertile as they are rich in the basic elements needed by plants.

Of course the final soil is always dependent on the climate and amount of vegetation matter.  For that reason, Hawaii for example – which is made up of 99% basalt – has a wide variety of soils including alpine soils and desert soils.


LIfe starts in a pile of volcanic cinder.

LIfe starts in a pile of volcanic cinder.

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About Gaz

I'm an Australian transplanted to rural Maine where I live on a small property with my wife and two youngest children. Life about family, work and trying the make the planet a better place for everyone.
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