Uniformitarianism-  Principle that states that the geological processes that operate today also operated in the past

Erosion- Process of wearing down and carrying away rocks

Weathering- Process that breaks down rock and other substances

Mechanical weathering- physically broken into smaller pieces

Chemical weathering- chemical changes that break down rock (e.g: acid rain)

Permeable-  material is full of tiny, connected air spaces that allow water to seep through it

Soil: the loose, weathered material on earths surface in which plants grow

Bedrock- solid layer of rock beneath the soil. 

Humus- decayed organic material (animal and plants) in soil

Fertility- measure of how well the soil supports plant growth

Loam- Soil with equal parts of sand, slit and clay

Horizon- a layer of soil that differs in color, texture, and composition from the layers above or below it 

O Horizon- thin, thick or not present in the soils.

A Horizon- topsoil mostly minerals from parent material with organic matter incorporated.

B Horizon- subsoil rich in minerals that leached from the A horizon lower limit of plant roots and burrowing animals

C Horizon- weathered /aged parent material, resembles parent material 

Decomposer- An organism that feeds on and breaks down dead plant or animal matter.

Natural resource- is anything in the environment that humans use. 

Contour plowing- farmers pillow their fields along the curves of a slope instead of in straight rows.

Conservation plowing- dead weeds and stalks of the previous years crop are plowed into the ground to help return soil nutrients, retain moisture, and hold soil in place.

Crop rotation: a farmer plants different crops in a field each year

Fossil- Preserved remains or traces of living things

Compression fossil- two-dimensional organic remains.

Impression fossil- two-dimensional but do not contain any organic matter

Petrified- turned to rock minerals replace the organism in the fossils.

Relative age- age of rock compared to the age of other rocks

Absolute age- the number of years that have passed since the rock formed

Strata-layer of rock

Principle of superposition- younger strata are on top, while old strata on bottom

Index fossil- fossils that help geologists match rock layers

Unconformity- a gap in geologic records. 

Half-life- a radioactive element is the time it takes for half of the radioactive atoms to decay.

Geological time scale- a record of the geologic events and the evolution of life forms as shown in the fossil record

Eras- earths history has been divided into 4 eras

Periods- a row of chemical elements.

Precambian- technically not an era referred to as a time 

Paleozoic- Era of ancient life, 

Mesozoic- the era of geologic time

 Cenozoic- recent life