Download chapter 7, section 2

SECTION 2 NATURE OF SOIL
FORMATION OF SOIL
• A MIXTURE OF WEATHERED ROCK, DECAYED
ORGANIC MATTER, MINERAL FRAGMENTS, WATER
AND AIR
• CAN TAKE THOUSANDS OF YEARS TO DEVELOP –
EITHER THICK OR THIN
FACTORS AFFECTING SOIL DEVELOPMENT
• CLIMATE
• SLOPE OF LAND
• TYPES OF ROCK
• TYPES OF VEGETATION
• AMOUNT OF TIME ROCK HAS BEEN WEATHERING
• SOIL IN TROPICAL REGIONS IS DIFFERENT THAN
THAT IN A POLAR REGION
• SOIL FORMED ON STEEP SLOPES IS THINNER THAN
THAT FORMED ON FLAT LAND
COMPOSITION OF SOIL
 DECAYED PLANT AND ANIMAL MATERIAL FORMS
DARK HUMUS – PROVIDES NUTRIENTS
SOIL PROFILE
 THE THREE LAYERS OF SOIL – CALLED HORIZONS
(A, B AND C)
A HORIZON
• TOP LAYER OR TOPSOIL
• COVERED WITH LITTER-BITS OF LEAVES, TWIGS
AND OTHER ORGANIC MATERIAL THAT BECOMES
HUMUS
• DARK AND FERTILE
B HORIZON
•
•
•
•
•
BELOW A HORIZON
NO LITTER
LIGHTER IN COLOR THAN A HORIZON
LESS FERTILE
CONTAINS MINERALS LEACHING FROM THE A
HORIZON
C HORIZON
• BOTTOM HORIZON
• CONSISTS OF PARTIALLY WEATHERED ROCK
• NOT MUCH ORGANIC MATERIAL
• THICKEST HORIZON
• NOT AFFECTED BY LEACHING
• BELOW C IS MOSTLY PARENT ROCK
GLACIAL DEPOSITS
• MANY PLACES ON EARTH ARE COVERED BY
MATERIALS DEPOSITED BY GLACIERS
• THESE DEPOSITS ARE VERY FERTILE
SOIL TYPES
• SOIL IS NOT THE SAME EVERYWHERE
• CLIMATES AFFECT THE TYPE OF SOIL
• DRY AREA MEANS LESS PLANTS AND HUMUS
• WET CLIMATE MEANS MORE FERTILE SOIL
OTHER FACTORS
• PARENT ROCK – TYPE OF ROCK AFFECTS TYPE OF
SOIL ABOVE IT
• TIME WEATHERING – LONGER TIME LESS ROCK
• SLOPE – STEEP SLOPE MEANS POOR SOIL,
BOTTOMLANDS HAVE RICH SOIL