Relative aging, fossils, natural disasters

The Changing Earth

Create 3 Venn diagrams comparing different types of erosion. You must include 3 different facts for each one. Worth 27 points.

Example:

HOMEWORK

Wind3

facts

Water3

facts

3 facts

Rocks breaking down into smaller pieces

Erosion

Water that moves over Earth’s surface

Causes sheet erosionMoves downhillForms rills and gullies

Runoff

Erosion creates valleys, waterfalls, flood plains, meanders, oxbow lakes

Deposition creates alluvial fans, deltas, add soil to flood plain

Rivers

Underground waterChemical weathering-water combines with CO2 to form carbonic acid, breaks down limestone

Forms caves, stalactite (roof) and stalagmite (floor)

Groundwater

Continental glaciers-covers much of continent, island

Valley glaciers-long, narrow glacier from snow and ice in mountain valley

Glaciers

Plucks rocksBreaks rocksDrags rocks which scratches bedrock

Deposits sediment when it melts- till, moraine, kettle

Glaciers

Energy comes from wind blown across water’s surface

Break apart rocks on shoreAbrasion-headland, arch, caveDeposit sediment-beaches, spits, sandbars, barrier beaches

Waves

Deflation-wind removes surface materials, Dust Bowl

Abrasion-Polishes rock, little erosion

Deposits-sand dunes, loess-sediment that is finer than sand

Wind

Soil

Loose, weathered material on Earth’s surface in which plants can grow.

Soil Formation

Rock broken down by weathering

Sediment mixes with materials on surface

Soil horizon-layer of soil that is different in color and texture

Soil Layers

Topsoil- crumbly, dark soil that is a mixture of humus, clay, and other minerals

Subsoil-Clay, other particles, little humus

Living Organisms in Soil

Humus-formed from organic material

Litter-layer of dead plant leaves

Decomposers-break down organic matter to form humus

Earthworms, and other burrowing animals mix soil

Importance of SoilFertility-ability for plants to grow depend

on nutrients in soil

Dust Bowl-loss of topsoil, devastating

Soil conservation by farmers

Fossils

Preserved remains or traces of living things

How fossils form

Living things die and are buried in sediments

Sediments harden into rock and preserve shapes of organisms

Sedimentary rock

Molds and castsMost common

Mold-hollow area in sediment in shape of organism

Cast-sold copy of the shape of organism

Petrified FossilsMinerals replace all or part of an organism

Petrified wood

Carbon FilmsExtremely thin coat of carbon on rock

Carbon from organism left behind in shape of organism

Trace FossilsProvide evidence of activities of organisms

Footprints

Trails

Burrows

Preserved RemainsOrganism trapped in tar, or amber

Rancho La Brea tar pits

Freezing in Siberia

Protects organism from decay

Age compared to the age of other rocks

Absolute age-number of years since rock formed

Relative Age of Rocks

In horizontal sedimentary rock layers, the oldest layer is at the bottom and each higher layer is younger than the layers below it.

Law of Superposition

Extrusion- lava that hardens on the surface◦ Always younger than the extrusion below it

Intrusion- Magma that hardens into igneous rock◦ Always younger than the rock layers around and

beneath it Faults-Break in Earth’s crust

◦ Younger than rock it cuts through Unconformity- Gap in geological record

◦ Rock layers lost because of erosion

Determining Relative Age

Tell relative ages of the rock layers in which they occur

Index Fossils

Atoms of one element break down to form atoms of another element

Half-life- time it takes for half of the radioactive atoms to decay

Carbon-14- measure amount of Carbon-14 left in organism to determine absolute age

Radioactive Dating