Physical Envi - soil

Question 1

“ Explain the main conditions and processes which have led to the formation of a gley soil. (7 marks)”

Answer 1

cold temperatures restrict decomposition of what limited vegetation there is - slow decay of mosses, lichens and marsh plants - form a dark and extremely shallow acidic Mor humus. Thawing of the ground surface in the short summer creates melt water which is unable to drain freely through the soil - this causes water logging. Alternative periods of freezing and thawing cause a lot of disturbance and mixing of the soil horizons, giving unclear horizons. The frozen sub soil layer in gley soils restricts drainage causing the soil to become saturated. Organism activity restricted due to cold temps. Water logging of the soil - results in a lack of oxygen which further restricts organism activity. The B and C Horizons often contain fragments of parent rock which has been broken up through freeze thaw weathering.

Question 2

Describe Gley soil horizon structure

Answer 2

Found in flat area prone to water logging - slow decay due to cold conditions

Shrubs and shallow roots
1) horizon A - black with acid humus - rocks
2) horizon B - waterlogged blue grey, clayey mud - rocks
3) horizon C - permafrost
4) horizon D - bedrock

Horizons are mixed and not well defined

Question 3

Describe Podzols horizon structure

Answer 3

Coniferous forest with short cool summers
Raw acid humus (mor) just bellow soil
1) horizon A - shallow roots - mineral organic layer
2) horizon E - ash grey eluviated layer
Extra - iron pan
3) horizon B - reddish brown layer
4) horizon C - parented rock broken down from freeze thaw weathering

Question 4

Describe Brown earth horizon structure

Answer 4

Leaf debris
Mild acid humus containing plant food
1) horizon A - dark brown layer - deep roots with lots of minerals
Merging boundarie
2) horizon B - brown layer with roots to take up minerals
3) horizon C - lightest layer of weathering parent material

Question 5

Explain podzol soil

Answer 5

Parental horizon is deprived from glaciers. The rocks break down from freeze thaw weathering because of the climate of the tiger biome, its cold.

They Ash grey horizon is ash grey because the water from rain precipitates onto the ground and travels through the soil in percolation. It deprives the upper layer of nutrients as the water reacher the iron pan and takes away the natural colour of the horizon above it.

There is a layer needles and moss because the needles from the trees have a thin wax layer therefore they do not erode quickly once they fall off the trees as they are well protected. This causes the needles to collect and create a layer above the soil. Another reason is the climate and due to the cold temperature erosion does not occur quickly, instead the needles freeze.

Question 6

Explain brown earth soil

Answer 6

Brown Earth exists in temperate locations such as Western Europe, with mild/warm climates. These climates break down/decompose deep leaf litter quickly in the A horizon meaning the mull humus is rich in nutrients.
Humus production can also be positively affected by South facing slopes that get more sunlight and higher temperatures
The deep roots of the plant/tree life in these areas means minerals are recycled back to the vegetation, this combined with the copious soil biota and organisms, such as worms, mean the soil is well aerated and does not allow distinct horizons to form.
As precipitation slightly exceeds evaporation, leaching occurs and can create an iron pan which limits drainage. Linked to this, weathering of the parent material in the R horizon can alter the soil, where hard rocks such as schist take longer to break down, producing thinner soils.
Thinner soils can also be produced by steep sloped areas where gravity causes soil to move downhill.

Question 7

Command word annotate

Answer 7

Don’t explain, just describe