Soil Production Breaks Geologic Speed Record
Geologic time is shorthand for slow-paced. But new measurements from steep mountaintops in New Zealand show that rock can transform into soil more than twice as fast as previously believed possible.
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“Geologist [I'm Climate Change]”
Since: Mar 07
#1 Feb 3, 2014
As a graduate geologist, I have actually been interested in the mechanism of making soil personally. A very handy thing to do in an area subject to soil creep, erosion, and very resilient hornfels metamorphosed shale in between remnant cumulate filled sills formerly underlying a large stratovolcano complex.
While the hornfels lasts as ground up particles for decades after being reduced with a bit of grunt with a hammer, other substrates become soil much faster.
Concrete reduced to an average of 3mm or less is part of the soil column in 10 years or less if it is spread thinly over the pre existing soil & grass is able to grow through it. As an aside: if the powder is spread thinly it is an excellent lawn sand, good for liming grass in acid soils. If it is spread in a plate over 3cm thick it tends to self cement into a flexible pavement similar to the ground limestone pavements seen in parkland. There is a lot of old concrete & is quite capable of being used in the same way as limestone paving which tends to be expensive as the quarries tend to get worked out fairly quickly.
Concrete as a thin layer is also surprisingly good as a to dressing under oak trees, it apparently neutralises gallic acid which is good for worms & therefore by proxy good for the tree.
Brick reduces to a red powder most of the time, with big bits to 3mm reducing by frost & wormy action in less than 3 years. being full of unstable minerals it is also very good at making plants grow. Particular successes with brick bits are young & establishing rosaceous fruit trees but it behaves like neutral volcanic ash with practically every plant species. A handy thing to know if the builders have left a few chunks behind in the soil column.
Volcanic rocks tend to last almost as long as hornfels and slates but the surface area to volume ratio apples with the result that they become a more than ususlly fertile sand (a bit like beach sand without the salt).
Glauconite sandstone given the mosh treatment tends to self cement like concrete when laid thick but reacts in the same way as powdered concrete when laid thin. It is soil in 10 years and is a fairly light coloured loam, which will darken with age & addition of worm poo.
Red sandstone tends to be rich in weathered feldspar & is usually cemented by calcite. This becomes an excellent lawn sand when laid over grass in thin layers as it adds both calcite & also Na & K rich clay which is handy for the grass, & as much iron as an average red brick. The clay tends to be illite, sub illite & kaolinite so the resulting clay plate is not porous. If the soil is non porous puddle clay it is best to use brick & concrete which adds minerals & porosity to the soil.
Shales are soft by nature. those that are almost slate are resistant to weathering & end up as flat sandy & silty plates with minerals released slowly from the edges of the grains. Most mechanical breakup of softer shales is a mixture of frost & gravity with the result most of the time of soil formed as a layer on top of a pristine mudstone or shale.
For a soft mudstone such as the red Mercian mudstone (a sub illite puddle clay impervious to water), soil is best made by addition to the substrate as pristine clasts wash out in rain into a flat lying slip which being impermeable tends to smother & exclude oxygen from the soil underlying the slip. Addition of anything porous in this case will deepen the soil layer & being sub illite anything with minerals in it will improve the fertility. Expect a soil of worth from fresh mudstone in 30 years or so but also expect the volume thickness to rise by a few centimetres & also expect flood puddles In heavy rain.
Black shales rich in carbonaceous goo are best improved by mix of both brick & concrete. At that point the organic goo provides enough humus from kerogen & oxygen to gain a bacterial flora which rapidly develops a wormy ecosystem. This will be a 20 year soil job.
Have a nice day: Ag
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