sequence of layering of the rocks and the evolution of life
natural radioactivity of chemical elements in rocks
Eon -> Era -> Periods -> Epochs -> Stages
Cretaceous Period: development of flowering plants. Large diversity in dinosaurs but ending withe their sudden extinction approximately 65 million years ago. Formation of the Andes Mountains. African and South American plates begin to separate. Climate is cooling. Shallow seas are prominent."
Key principles:
rock layers (strata) are laid down in succession. With each strata representing a "slice" in time
Superposition: the higher the layer, the newer/younger it is
However, this scale can still be compromised by erosion, and layers laid down in different places at the same time look different, and a layer only represents a part of Earth's history
Earth's Structure
Earth was formed 4.6 billion years ago
Three sections of the Earth:
Biosphere: all forms of life both on land and in sea
Hydrosphere: all forms of water (fresh, saltwater, snow/ice)
Internal Structure: divided into crust, mantle, and core
crust is 0.5% of Earth's mass
split into basalt rich oceanic crust and granite rich continental crust
Continental Crust is composed of volcanic, metamorphic, sedimentary, and granite-type rocks
The Moho is the boundary between the crust and the mantle
The Mantle is solid, and the upper-third of it is the Asthenosphere, which is plastic-like
Lithosphere: brittle upper portion of the mantle and the crust that is always slowly moving
tectonic plates make up the Lithosphere
The Core: composed mostly of iron
outer core - molten
inner core - solid
Plate Tectonics
Continental Drift Theory
In 1915, Alfred Wegener proposed the existence of Pangaea
The evidence:
Fossilized tropical plants in Greenland's ice caps
Continents fit together like a puzzle
Similarities existed in the rocks between east coasts of the North and South America and the west coasts of Africa and Europe
Fossils of the same extinct land animals were found on separate land masses
Tropical climates used to be polar based on the climatic data of the region
Seafloor Spreading Theory
rocks got older as they moved away from the ridge
new crust being created at volcanic rift zones
Subduction Zones: areas on Earth where two tectonic plates meet and move toward each other, with one sliding underneath the other and moving down into the mantle
Three Types of Plate Boundaries:
Transform Boundaries
plates frequently slide past each other
frequently cause earthquakes
Example: San Andreas Fault
Convergent Boundaries
plates slide toward each other
forms either a:
Subduction zone - one plate slides underneath
Orogonic plate - two plates collide and compress
Example: Cascade Mountain Range
Divergent Boundaries
plates slide apart from each other
space between is filled with magma
Example: Mid-Atlantic Range, East Pacific Rise
Convergent Boundaries can create different things depending on the crust Continental-Continental -> Mountain Range Oceanic-Continental -> Volcanoes Oceanic-Oceanic: Island Arc (ex: Japan)
Earthquakes
occur during abrupt movement on a fault
energy held in place by friction is released
Vocab:
Focus: area where energy is released
Epicenter: directly above the focus, on the surface
Seismic Waves: waves that travel outward
measured on the Richter Scale, recorded by the Seismograph onto a Seismograph
The Richter Scale goes up by a tenfold increase of amplitude, and 32x the energy
The severity of an earthquake depends on:
The amount of potential energy stored
Distance the rock moved
How far below the surface
Makeup of the rock material
Two types of Seismic Waves:
1. Surface Waves
produce rolling/swaying motion
slower, cause ground motion and damage
2. Body Waves
P Waves
travel through the Earth
caused by expansion and contraction of bedrock
S Waves
material moves Vertically or Horizontally
travel only in the uppermost layers
Tsunamis
series of waves created when a body of water is rapidly displaced (usually by an Earthquake in a subduction zone)
Volcanoes
classified as Active, Dormant, or Extinct
95% of volcanoes occur at subduction zones and mid-oceanic ridges
other 5% are at hot spots where magma is near the surface
gases most commonly released by volcanoes are steam, carbon dioxide, sulfur dioxide, and hydrogen chloride
Sulfur dioxide is converted to sulfate ions in the stratosphere
can decrease global temperature
usually turn into acid rain after staying the atmosphere for 2 years
Safety with Volcanoes:
better volcanic prediction, magnetic changes, changes in seismic activity, measuring changes in temperature and gas composition, evacuation plans, and study of precursors
(click on the picture above for a "Parts of a Volcano" worksheet)
Seasons
determined by the tilt of Earth's axis (23.5 ° )
Earth is closest to the sun in December, January, and February
Earth is farthest away from the sun during June, July, and August
Seasons are NOT caused by Earth's distance from the sun -> actually by the angle of sunlight
Soil
soil components: air, water, minerals, and organic matter
It develops in response to:
Parent Material - rock and materials that the soil came from
Climate - partial weathering of parent material measured by temperature and precipitation
Living Organisms - bacteria, worms, snails, etc -> decompose
Topography - physical characteristics: drainage, elevation, and wind exposure
(click on the picture to the left for a Soil Horizons worksheet)
Soil Horizons is a layer parallel to the crust, with each horizon having their own unique characteristics. Depending on the soil component, there are usually three or four soil horizons. Soil Horizons are defined by physical characteristics like texture and color.
Igneous Rock formed by cooling of silica content solidify deep underground large grained texture (intrusive) fine grained texture (extrusive) becomes soil Metamorphic Rock formed by heat and pressure ex: diamond, marble, slate, coal, etc Sedimentary Rock formed by piling of various materials over time fossils are only trapped in this rock