The Dynamic Earth Chapter 3

Earth consists of: Rock – geosphere Air – Atmosphere Water – hydrosphere Living things (organisms) - biosphere

The Earth as a System

Geosphere All the rock that makes up the solid part of the Earth and all of the loose rock and soil on the Earth’s surface

Geosphere Divided into three layers based on composition: Crust – thin, outermost layer (lowest density) Mantle – next layer, made up of rocks of medium density Core – center and innermost layer, made up of the highest density

Divided into five layers based on physical structure: Lithosphere – outer layer, rigid, includes crust and upper mantle, divided into pieces called tectonic plates. Asthenosphere – made of the mantle, solid, flexible and made of rock, allows plates to move on top of it.

Geosphere Five layers continued… Mesosphere – lowest part of the mantle Outer core – dense liquid layer Inner core – dense, solid and extremely hot See figure 3, page 65

Earth’s Layers

Plate tectonics Definition: is the movement of large pieces of the lithosphere (plates) on top of the asthenosphere Continents are located on top of plates and move along with them.

Major Plates: North America Pacific South America African Eurasian Antarctic See figure 4, page 66

Tectonic Plates

Most geologic activity takes place at the point where two plates meet – plate boundaries (faults) Collisions cause the crust to be pushed up forming mountains Earthquakes - cause breaks in the rock at faults which causes vibrations in the crust Magnitude of an earthquake is the amount of NRG released and this is measured by the Richter scale. The smaller the magnitude of the vibration, the weaker the earthquake. See Figure 6, page 67

Where do Earthquakes Occur?

Plates continued… Movements of the plates can cause molten rock or magma to flow upward through a volcano Volcanoes put large amounts of very hot ash, gasses and dust into the air Can reduce the amount of sunlight reaching Earth’s surface for long periods of time causing temperatures to drop over large areas. See Figure 7, page 68

Volcanoes: The Ring of Fire

Erosion: the removal and transport of materials on Earth’s surface. Caused by two main agents: Wind Water

Atmosphere Mixture of gases that surround the Earth and insulates the surface Made up of 78% - Nitrogen, 21% - Oxygen, 1% - other gases and tiny solid particles called atmospheric dust. Pulled toward the surface by gravity and is denser near the Earth’s surface

Divided into four layers based on temperature and distance from the surface: Troposphere – layer closest to surface, densest layer, most weather occurs here, temperatures decrease as altitude increases. Stratosphere – next layer, temperatures increase as altitude increases, contains ozone layer which blocks sun’s UV rays

Atmosphere layers continued… Mesosphere – next layer, coldest layer. Thermosphere – uppermost layer, highest temperatures, lowest part is called ionosphere.

Layers of the Atmosphere

Energy comes from sun and into the atmosphere and: 5% is reflected by Earth’s surface 20% is absorbed by clouds, ozone, and atmospheric gases 25% is scattered and reflected by clouds and air 50% is absorbed by the Earth’s surface

Energy is transferred through the atmosphere in three different ways: Radiation – transfer of NRG across space Convection – transfer of heat by air currents Conduction – flow of heat from a warmer object to a colder object by direct contact

Energy Transfer in the Atmosphere

Greenhouse effect Certain gases in the atmosphere (greenhouse gases) absorb some of the heat reflected by the surface preventing it from escaping back into space. Without it, Earth too cold for life Major greenhouse gases – carbon dioxide, methane, nitrous oxide and water vapor

The Greenhouse Effect

Hydrosphere Includes all water on or near Earth’s surface Water or Hydrologic Cycle – the continuous movement of water into air, onto land, and back into water sources.

Made up of three major processes: Evaporation – changing of a liquid into a gas-water to water vapor (occurs at the surface) Condensation – changing of a gas into a liquid Precipitation – water that falls from clouds in any form ex rain, snow, etc. See Figure 17, page 77

The Water Cycle

Two major types of water: Salt water or oceans 97% of all Earth’s water is here Contains salts (mostly sodium chloride) that have been dissolved out of rock, carried by rivers or come from volcanic eruptions Average salinity – concentrations of salts is 3.5%

Four major oceans Indian Atlantic Pacific (largest, deepest) Artic (smallest) Actually all joined into one world ocean Covers 70% of Earth’s surface See Figure 18, page 79

Earth’s Oceans

Oceans Divided into zones based on temperature: Surface – warm, top layer Thermocline – middle layer where temperature drops rapidly with depth Deep Zone – bottom layer, extremely cold, no light

Oceans continued… Ocean regulates world temperature by absorbing and storing sun’s NRG and then moving the NRG around using currents Without this temperature regulation, Earth’s temperatures would be too extreme to support life.

Oceans continued… Surface currents – stream like movements of water near the surface, driven by the wind, can be warm or cold and they don’t mix easily. Deep currents – stream like movements of water near the bottom of the ocean, form when cold dense water drops below warmer less dense water, flow extremely slow

Temperature Zones

Fresh Water Lakes, rivers, wetlands, groundwater, glaciers and ice caps 3% of all water Most in ice caps and glaciers Rivers – flowing water Lakes – standing water Groundwater – water that trickled down through the soil and rock

Groundwater continued… Collects in aquifers – rock layers that surround and collect groundwater Recharge areas – land that supplies groundwater to an aquifer See Figure 24, page 83

Aquifers

Biosphere Layer of Earth which supports life Very thin Extends 12 km below the ocean and 9 km into the atmosphere Most life requires: Liquid water Moderate temperatures NRG source (food) Continuous recycling of all needed materials Gravity

All NRG for life supplied originally by the sun and is transferred up the food chain Plants use light NRG to make food; plant is eaten by an animal and that is eaten by another animal, etc. At each step in the food chain some NRG is used and lost, only about 10% goes onto the next step Earth is a closed system – NRG can enter (light) and leave (heat), but matter cannot