Looking at the Earth

Chapter 2

Nebular Hypothesis

“3rd rock from the sun……”

4.6 billion years ago

…..and then…..

Pangaea

Today

Actually it has a pole-to-pole circumference of 40,007km and an

equatorial circumference of 40,074km

Our Earth

• Mostly rock

• 71% global ocean (hydrosphere)

• Oblate spheroid

• “Little” change in topography– 20km compared to a diameter of 12,756km

Earth’s Interior

A Magnet?

All magnetic objects produce invisible lines of force, extending between the poles of the object. Note that I said the lines were INVISIBLE. An easy way to see these invisible field lines is to spread iron filings on a sheet of paper and place a bar magnetic under the paper. The iron filings will arrange themselves around the magnet and along the magnetic field lines. The earth acts like a very large magnet. Just as a bar magnet produces field lines, so too does Earth. And, just as the magnetic field of a bar magnet pushes iron filings into a pattern, so too does the Earth's magnetic field. That is why a compass always points North. You can visualize the Earth's invisible magnetic field lines by thinking of the Earth as having a bar magnet

running from the North to South poles.

It just so happens that our Sun sends more than light to the Earth. Besides light, the sun sends tiny, little pieces of matter to the Earth. These pieces of matter are moving very fast when they come close to the earth. In fact, they are moving so fast that scientists call this the SOLAR WIND.The solar wind "squashes" the earth's magnetic field. As you can see in the picture that follows, the magnetic field lines on the sun side of earth (left) are squashed and on the side of the earth away from the sun (right), the magnetic field lines

are stretched out as if the wind is trying to blow them away.

A connection?

Our planet is connected with our sun with more than light. In this picture, it appears the sun and earth are connected by the stream of charged particles that come from the sun. The Sun produces a hot gas that travels through space at a million miles per hour, carrying particles and magnetism outward past the planets. In essence, the Earth is immersed in the Sun's atmosphere. Changes on the Sun affect the solar wind flow; for example, solar flares, which are explosions associated with sunspots, cause strong gusts of solar wind.

During periods of gusty solar wind, powerful magnetic storms in space near the Earth cause vivid auroras, radio and television static, power blackouts, navigation problems for ships and

airplanes with magnetic compasses, and damage to satelites and spacecraft. Events on the Sun and in the magnetosphere can also trigger changes in

the electrical and chemical properties of the atmosphere, the ozone layer, and high-altitude

temperatures and wind patterns.

• We've learned that the solar wind travels past the Earth at well over 1,000,000 miles per hour. And thanks to the Earth's magnetic field, the solar wind is stopped and deflected around the Earth so that most of it does not hit our atmosphere head on.

When the solar wind comes to the earth it meets the Earth's magnetic field. Most of the tiny particles in the solar wind are pushed around the earth because of this magnetic field. They begin their journey around in a curve called the "Bow Shock". Just like water makes a curved wave in front of a boat, the solar wind makes a curve in front of the Earth. Afer passing through a shock wave at the bow shock, the wind flows around the magnetosphere and stretches it into a long tail. However, some solar wind particles leak through the magnetic barrier and are trapped inside. Solar wind particles also rush through funnel-like openings (cusps) at the North and South Poles, releasing tremendous energy when they hit the upper atmosphere. The Northern and Southern Lights (auroras) are the evidence we can see of this energy transfer from the Sun to the Earth. The particles then follow a path that goes around the earth in a sort of cover or sheath. This curve is called the "magnetosheath". These particles mix with other particles that come up from the earth's ionosphere to fill the magnetosphere. A great many of the tiny pieces of matter in the earth's magnetosphere don't come from the sun's solar wind. They come from the earth. Our planet can lift air particles into space and these particles will become charged by the time they get there.

The Magnetosphere

Gravity

Gravity• Force of attraction between

all matter

• Newton’s Law of Gravitation– Force of attraction between 2

objects depends on their masses and the distance between them

– The larger the masses or the closer they are, the greater the force of gravity between them. Weight is a measure of the pull of gravity (your weight is 0.3% less at the equator).

Gravity (continued)

• Newton (N) is measure of SI weight– N = kg X m/s2

– Weight depends on its mass and distance from the center of the Earth

– Mass is amount of matter– Weight changes with location, mass does not– Kg of mass weighs about 10 newtons on the

surface of the earth

Systems

• An organized group of related components that interact to create a whole

• Subatomic to the universe

• Boundaries

• Many have matter/energy flowing through

• All are linked

Earth Systems• Interaction of 2 basic

components– Matter (has mass &

occupies space)– Energy (ability to do

work)

• Closed systems – energy, not matter, is exchanged with environment

• Open systems – both energy and matter exchanged

• Earth is technically open, but realistically closed with little matter entering or leaving

4 Spheres

• Atmosphere – blanket of gases

• 78% nitrogen• 21% oxygen• 0.03% carbon dioxide• And others

– Argon– Water vapor– Helium– ozone

4 Spheres

• Hydrosphere – Earth’s water (except atmospheric vapor)

• 71% of Earth’s surface• 97% of that is ocean,

3% fresh• Fresh includes

– Lakes, ponds, streams and rivers

– Glaciers and ice sheets– Groundwater in soil and

rock

4 Spheres

• Geosphere – the mostly solid part, including rock, soil, molten interior and ocean floor

• Continuously recycled by subduction and volcanism

4 Spheres

• Biosphere – all forms of life in other spheres

• Decaying organic matter

• From deepest ocean to a few km above the Earth’s surface

Earth’s Energy Budget

• Energy is transferred between systems, but is neither created nor destroyed (1st Law of Thermodynamics)

• Budget – additions balanced by subtractions

• When energy is transferred, matter becomes less organized and is spread out more uniformly over time (2nd Law of Thermodynamics)

• Stored and moved by reactions

Internal Energy Sources

• Radioactive decay• Earth’s formational

heat• Convection circulates

heat and molten rock– Drives the motion of

the crustal plates, too

External Energy Sources

• Solar radiation heats geo/atmosphere for winds and circulation

• Sun powers photosynthesis

• Gravitational energy of moon and sun runs tides and currents

Biogeochemical Cycles

Cycles in the Earth System

Humans and Earth Systems

• Natural cycles altered by man’s activities– C (fossil fuels)– N/P (agriculture and

development)– Water (pollution and

global warming)

Ecology

• Study of relationship between various organisms and their surroundings (biotic and abiotic). Oikos and logos = ecology

• Ecosystem = community of organisms and the natural environment they inhabit

• Carrying capacity = largest population any environment can support at one time

• Ecosystems react to changes to maintain or restore a balance

Energy Transfer

Food chains

Food Webs