What is soil made of? Weathered rock Organic material (humus) Air Soil has 4 components: Weathered rock Organic material (humus) Air Water

Soil is formed from weathered rock and organic material (HUMUS) PARENT MATERIAL is what the soil forms from When the parent material is the underlying bedrock of the area the soil is called RESIDUAL SOIL (residual = what is left behind when the bedrock weathers) If the soil was formed in one place and carried elsewhere (by wind, water, glaciers, etc…) then the soil is called TRANSPORTED SOIL

Cross section of soil layers Each layer is called a HORIZON Horizon O/A = Topsoil (mostly Humus, some weathered rock) Horizon B = Mostly weathered rock, some organic material (mineral rich zone) Horizon C = Broken Bedrock BEDROCK

HORIZON A HORIZON B HORIZON C

IT TAKES 100-400 YEARS FOR 1cm OF TOPSOIL TO FORM!!!! Plants hold the soil together and prevent soil erosion

MOVEMENTS OF THE EARTH CAUSED BY THE FORCE OF GRAVITY MASS MOVEMENTS MOVEMENTS OF THE EARTH CAUSED BY THE FORCE OF GRAVITY

CREEP Very slow downward movement of soil Only noticeable by the results of trees, fence posts, telephone poles, etc… that are tilted downhill

LANDSLIDE RAPID mass movement of soil downhill (usually a very steep slope) AVALANCHE – landslide made of Ice & Snow as well as Soil SLUMP – small areas of land move downhill - especially along roadways that cut into the side of hills

Baltimore, Maryland Landslide

MUDFLOW or LAHAR Very fast & Dangerous movement of water saturated soil (MUD)

Even though rapid mass movement is more noticeable than slow mass movement, overall, more material is transported via creep than all others combined