Global Warming - Part 1

Earth has warmed by about 1 F over the past 100 years. But why? And how? Well, scientists are not exactly sure. The Earth could be getting warmer on its own, but many of the world's leading Climate scientists think that things people do are helping to make the Earth warmer.

Greenhouse Effect, Climate Change,
and Global Warming

The Greenhouse Effect: Scientists are sure about the greenhouse effect. They know that greenhouse gases make the Earth warmer by trapping energy in the atmosphere.

Climate Change: Climate is the long-term average of a region's weather events lumped together. For example, it's possible that a winter day in Buffalo, New York, could be sunny and mild, but the average weather – the climate – tells us that Buffalo's winters will mainly be cold and include snow and rain. Climate change represents a change in these long-term weather patterns. They can become warmer or colder. Annual amounts of rainfall or snowfall can increase or decrease.

Global Warming: Global warming refers to an average increase in the Earth's temperature, which in turn causes changes in climate. A warmer Earth may lead to changes in rainfall patterns, a rise in sea level, and a wide range of impacts on plants, wildlife, and humans. When scientists talk about the issue of climate change, their concern is about global warming caused by human activities.

WEATHERING AND SEDIMENTARY ROCKS

WEATHERING AND SEDIMENTARY ROCKS

Weathering - Process which acts at the earth's surface to decompose and breakdown rocks.

Erosion - The movement of weathered material from the site of weathering. Primary agent is gravity, but gravity acts in concert with running water.

Types of Weathering

1. Mechanical or Physical - the breakdown of rock material into smaller and smaller pieces with no change in the chemical composition of the weathered material.

2. Chemical - the breakdown of rocks by chemical agents. Obviously the chief chemical agent is water which carries dissociated carbonic acid.

Mechanical Weathering

1. Expansion and Contraction - the thermal heating and cooling of rocks causing expansion and contraction.

2. Frost Action - Water freezes at night and expands because the solid occupies greater volume. Action wedges the rocks apart. Requires adequate supply of moisture; moisture must be able to enter rock or soil; and temperature must move back and forth over freezing point.

3. Exfoliation - process in which curved plates of rock are stripped from a larger rock mass. Example Half Dome. Exact mechanism uncertain but probably due to unloading.

4. Other types - Cracking of rocks by plant roots and burrowing animals.

Chemical Weathering

Factors which effect the rate of chemical weathering are:

• Particle size - Smaller the particle size the greater the surface area and hence the more rapid the weathering

• Composition

• Climate (See Figure)

• Type and amount of vegetation

Chemical Weathering of Rocks

Show Figure and explain formation of carbonic acid

H₂O + CO₂ ------->> H₂CO₃

Acid then dissociates and the following happens:

2KAlSi₃O₈ (feldspar)+ 2H⁺ + H₂O ------->> Al₂Si₂O₅(OH)₄ (clay)+ 2K⁺ + 4SiO₂

Weathering of Igneous Minerals

Products of Weathering Figure:

1. Quartz - slow process and largely ineffective. Quartz remains quartz. Grains are rounded.

2. Feldspar - weathers to clay with the cations Na, Ca, and K going into solution. Clays that can form include kaolinite (pure aluminum silicate), illite and montmorillonite. Factors which dictate clay formation are (a) climate; (b) time; (c) parent material.

3. Muscovite - Same as above

4. Ferromagnesian minerals - weather to clay plus highly insoluble iron oxides, essentially varieties of limonite (rust).

Rates of Weathering

Studied by S.S. Goldich (Figure) and found to be inverse of Bowen's Reaction Series. Why? A function of equilibrium, the higher the temperature of formation of a mineral the more unstable it is at the earth's surface. Hence olivine weathers the most rapidly.

Soils

Soil - Surficial material that forms due to weathering. Includes an organic component. Many different soil types. Factors effecting their formation are:

1) Climate

2) Relief

3) Bedrock material

4) Time

Classification of soils varies depending on the classifier. Geologists use a very simple classification based largely on materials added or removed from the soil during its formation.

Soil consists of four major zones (horizons) (Figure).

1. O horizon - Organic layer

2. A horizon - Zone of leaching - Cations are leached from this horizon by strongly acid solutions generated in the O horizon

3. B horizon - Zone of Accumulation - Cations leached out of the A horizon accumulate here. Horizon consists of clays, iron and aluminum oxides. Deposition due to neutralization of acid solutions.

4. C horizon - Partially decomposed parent material. Lower most zone.

Soil Types

Pedalfer - Named for the abundance of Al and Fe in the B horizon. Occur in temperate, humid climates. Lie generally east of the Mississippi River, correspond with 63 cm/yr rainfall contour.

Pedocal - Named for the accumulation of calcium carbonate in the B horizon. Characteristic of temperate, dry climates. Lie generally west of Miss River. Poorly developed A horizon, B horizon is caliche (calcium carbonate).

Laterites - Tropical soils thought to represent the end products of weathering. Characterized by stark red color and abundance of iron and aluminum oxides and lesser clay minerals. Requires abundant rainfall.

SEDIMENTARY ROCKS

Sedimentary Rocks - Layered or stratified rocks formed at or near the earth's surface in response to the processes of weathering, erosion, transportation and deposition.

Rock Cycle

All rocks discussed in this class are a part of the rock cycle (Figure).

Sedimentary Cycle (Figure)

Processes

1. Transportation - Transporting medium usually water. More rarely wind or glacial ice.

2. Deposition - Occurs when energy necessary to transport particles is no longer available. Deposition due to the gentle settling of mineral grains. Can also be result of chemical precipitation due to changing conditions.

3. Lithification - Involves several steps. All taken together are termed Diagenesis.

1. Compaction - Squeezing out of water.
2. Cementation - Precipitation of chemical cement from trapped water and circulating water.
3. Recrystallization - Growth of grains in response to new equilibrium conditions

Single most important characteristic of sedimentary rocks is layering. Occurs in response to changes in conditions at the site of deposition. Sedimentary rocks cover 75% of the earth's surface, but amount to only 5% of the outer 10 km.

Origin of Sedimentary Material

• Derived directly from pre-existing rocks. Ex. quartz.

• Derived from weathered products of these rocks. Ex. clay.

• Produced by chemical precipitation. Ex. calcite.

First two processes result in detrital or clastic rocks. Third produces nondetrital or chemical sedimentary rocks.

Minerals of Sedimentary Rocks

1. Clay - Important constituent of mudstones and shales, but occurs in minor amounts in all sedimentary rocks.
2. Quartz - Most abundant constituent of sandstone. In addition to detrital quartz, free silica can be chemically precipitated as opal, chalcedony and chert.
3. Calcite - Chief constituent of limestone. Precipitates from seawater which is saturated in both Ca⁺² and CO₃-2. Small changes in both T and P enough to cause precipitation. Differs from most compounds in that solubility decreases with increasing temperature.
4. Others

1. Dolomite CaMg(CO₃)₂ - Most important constituent of dolostone
2. Feldspars - Occur in sedimentary rocks formed by very quick deposition and burial allowing no time for feldspars to alter to clay.
3. Iron oxides and sulfides - Chemical precipitates dictated by the environment at the site of deposition.
4. Salts and gypsum - Chemical precipitates occurring in restricted sedimentary basins under arid climatic conditions. Modern analog is the Middle East (Red Sea).
5. Volcanic Debris - Glass and other pyroclastic material incorporated into sediments.

5. Organic Material - Forms coal and gives color to black shales.

Classification of Sedimentary Rocks

Texture - Size, shape and arrangement of particles.

1. Clastic - Formed from broken or fragmented grains (detrital). Rock appears grainy. Basis of classification of the clastic rocks is the Wentworth Size Scale which was derived from studies of grain diameters.

Wentworth Size Scale
Boulder	>256 mm	Conglomerate
Cobble	64-256 mm
Pebble	2-64 mm
Sand	1/16-2 mm	Sandstone
Silt	1/256-1/16 mm	Siltstone
Clay	<1/256>	Shale

Conglomerate - Detrital rock made up of more or less rounded fragments, an appreciable percentage of which are pebble size or larger

Sandstone - Consists primarily of grains in the sand size range. Dominant mineral in sandstones is always quartz. Further subdivide sandstones based on other minerals present. Quartz sandstone is 99% quartz. Arkose contains both quartz and feldspar. Graywacke is a garbage sandstone with quartz, feldspar, mica and rock fragments. Often has a significant fine-grained component and is poorly sorted.

Siltstone - Rare sedimentary rock composed mostly of silt sized particles. Rare because dominant mineral is quartz which does not like to get any smaller than sand size. Many siltstones thought to form by glacial grinding of sand-sized quartz grains.

Shale - Most common of the sedimentary rocks. Composed primarily of clay minerals. Often tends to split into flat sheets due to the mica-like cleavage of clay minerals.

2. Nonclastic (chemical) - Grains are interlocked through crystallization. Has igneous appearing texture with very little open space.

Limestone - Formed by the precipitation of calcite from seawater. Most form in marine environments, but also around hot springs, as a crust in desert soils, and as cave formation.

Dolostone - Composed of the mineral dolomite. Probably starts life as limestone then is altered to dolostone by Mg-bearing solutions in arid environments.

Evaporites - Formed by partial to complete evaporation of seawater in enclosed basins. Forms salts and gypsum.

Organic Rocks - Rocks formed by the accumulation of organic material. Ex. coquina and chalk.

Coal - Rock composed of lithified plant material.

Abundance of Sedimentary Rocks (Figure)

Sedimentary Structures (Figure)

A) Structures formed during deposition

1. Bedding - Layering of sedimentary rocks. Each bed represents a homogeneous set of conditions of sedimentation. New beds indicate new conditions. Most layering is parallel, but occasionally it is inclined. These inclined layers are cross beds. Examples of sedimentary environments in which cross beds form are dune fields and deltas.
2. Graded beds occur when a mass of sediment is deposited rapidly. The bedding has the coarsest sediment at the bottom and finest at the top. Often found forming in submarine canyons. A collection of graded beds is termed a turbidite deposit. Well exposed in many of the sea cliffs along So. Cal. beaches.
3. Ripple Marks - Waves of sand often seen on a beach at low tide and in stream beds.

a) Current - asymmetrical - Rivers

b) Oscillation - symmetrical - Beaches

4. Mud Cracks - Polygonal-shaped cracks which develop in fine grained sediments as they dry out. Common in arid environments, such as a desert.

B) Structures formed after deposition

1. Nodule - Irregular, ovoid concentration of mineral matter that differs in composition from the surrounding sedimentary rock. Long axis of the nodule usually parallels the bedding plane and seems to prefer certain layers.
2. Concretion - Local concentration of cementing material. Generally round. Usually consist of calcite, iron oxide or silica. Can exceed 1 meter in diameter. Not understood how they form.
3. Geode - Roughly spherical structures up to 30 cm in diameter. Outer layer consists of chalcedony. Inside lined with crystals. Calcite and quartz the most common.

C) Other features

1. Fossils - Any direct evidence of past life. Examples are dinosaur bones, shells of marine organisms, plant impressions, etc.

MINIBEASTS

Introduction

'Minibeasts' is a useful lay term to use when generally describing a broad group of small animals. However, it is more scientifically accurate to classify the animals we are looking at as arthropods.

The diagram below shows the scientific criteria used for classifying various 'minibeasts' into the large group called arthropods and its smaller sub-groups.

Examples of the arthropod sub-groups are:

• Insects include bees, butterflies, beetles, ants, moths, praying mantids, cicadas, cockroaches, fleas, wasps, and flies.
• Arachnids include spiders, scorpions, pseudoscorpions, ticks, and mites.
• Crustaceans include crabs, shrimps, prawns, lobsters, crayfish, and slaters.
• Myriapods include centipedes and millipedes.

Most arthropods have a hard exterior casing known as an exoskeleton, which they must shed in order to grow. This process is called moulting.

Insects

Insects have six jointed legs and a body that is divided into three parts: head, thorax and abdomen. Insects have a head that has a pair of antennae and have mouthparts that are adapted for particular diets. 75% of all animal species described by scientists are insects.

More information

• Why are most animals insects?

Points covered:

• Why are most animals insects?
• How did insects evolve to live on land?
• What is the evolutionary importance of being able to fly?
• What is the importance of the co-evolution of insects and plants?

Words to know:

• EPICUTICLE - the outermost layer of insects' exoskeleton.
• ARTHROPOD - the name for animals with jointed legs and an exoskeleton.
• TERRESTRIAL - pertaining to or living on land.
• SPECIATION - the process of evolving new species.
• IMPERMEABLE - water can't pass through.
• DEVONIAN PERIOD - approximately 410 - 362 million years ago.

Insects comprise 75% of all animal species that scientists have named and described, and most of these insects have wings. The key to insect success is their ability to survive on land and take to the air.

Insects have adapted well to the terrestrial environment, which demands that an organism must prevent excessive water loss from its body. Insects solved this problem by modifying many aspects of their structure, physiology and habits. For example, the exoskeleton of insects has a special outer layer, the epicuticle, which is impermeable. Also, insects evolved unique solutions to the pressures of breathing, excreting waste without losing too much water and moving about on land.

The evolution of wings is an obvious key to insect success and diversity because it means that most insects can disperse widely and escape unfavourable environmental changes. Flight also provides a means of escaping predators and allows insects to colonise new environments where they may exploit new food sources.

Fossils show that insects were among the first animals to invade land during the Devonian Period, about 400 million years ago. This permitted them to utilise food resources that had not previously been consumed, such as terrestrial plants. The co-evolution of insects and plants has been very important in the histories of both groups. For example, insect mouthparts have evolved specialisations for different styles of biting and sucking plant tissues. Also, the pollination of flowering plants by insects has led to fresh avenues for the speciation of plants.

Arachnids (spiders, scorpions, mites and ticks)

Arachnids have a body divided into two parts: the cephalothorax (head + thorax) and the abdomen. They have four pairs of walking legs and lack both antennae and wings. They usually have 8 simple eyes.

Spiders are arachnids that have chelicerae (jaws with fangs) that inject poison, and they possess silk glands and spinnerets on the abdomen.

Scorpions, mites and ticks are also part of the Arachnid family. Scorpions have a long tail that ends in a stinger. They also have a pair of pedipalps (front limbs) that end in grasping pincers at the front of their bodies.

Most ticks and mites are parasites on other animals. A parasite is an animal that lives off the blood, body fluid or tissues of another animal. However, some mites feed on plant material rather than on animals.

More information

• Spider Fact Sheets
  http://www.amonline.net.au/factsheets/index.htm#spiders
• Scorpions Fact Sheet
  http://www.amonline.net.au/factsheets/scorpions.htm

Centipedes and millipedes

Most centipedes have 20 - 30 pairs of legs. A very few have as many as 100 legs. Centipedes are carnivores that catch other invertebrates for food. Large centipedes may sometimes even eat vertebrates such as frogs, geckos and mice. Centipedes have fangs which inject venom into their prey. Don't touch a centipede as it can give a painful bite.

Millipedes are herbivores. They feed on vegetable matter and are found in moist places such as under logs. They have hundreds of tiny legs that move together in waves to carry the millipede along. They don't have venom but some species produce an irritating fluid.

More information

• Centipedes
  http://www.amonline.net.au/invertebrates/other/index.htm

Crustaceans (crabs, shrimps and slaters)

All crustaceans have a body divided into a head, thorax and abdomen, and have more than eight legs. Most of them have a harder section protecting the thorax called a carapace. Many crustaceans live in water (both fresh and saltwater). Slaters are the most obvious crustacean that lives on land. You can find these in your backyard - check under pot plants and logs. Australia has at least 7 species of freshwater crab and many more species of saltwater crab.

More information

• Crustaceans
  http://www.amonline.net.au/invertebrates/cru/index.htm

Rotation and Revolution

Planet Earth in Motion offers an exciting perspective on the motion of Earth and how it relates to time. Segment 1 is about the sun and Earth.

Although often confused, there is a distinct and important difference in the concepts of revolution and rotation. Earth rotates on its axis as it revolves around the Sun.

Earth rotates about its axis at approximately 15 angular degrees per hour. Rotation dictates the length of the diurnal cycle (i.e, the day/night cycle), creates "time zones" with differing local noons, and also causes the apparent movement of the Moon, stars, and planets across the "celestial sphere". The rotation of Earth is eastward (from west to east) making the apparent rotation of the celestial sphere from east to west.

The rates of rotation and revolution are functions of a planet's mass and orbital position. For example, the mass of Jupiter is approximately 317.5 times Earth's mass and the rotation time (the time for Jupiter to revolve once about its axis) is approximately nine hours.

Earth takes approximately 365.25 days to complete one revolution around the Sun in a slightly elliptical orbit with the Sun at one focal point of the ellipse. Ranging between the extremes of perihelion (closest approach) in January and aphelion (most distant orbital position) in July, Earth's orbital distance from the Sun ranges from approximately 91.5 to approximately 94 million miles (147–151 million km), respectively. Although these distances seem counterintuitive to residents of the Northern Hemisphere who experience summer in July and winter in January—the seasons are not nearly as greatly affected by distance as they are by changes in solar illumination caused by the fact that Earth's polar axis is inclined 23.5 degrees from the perpendicular to the ecliptic (the plane of the solar system through or near which most of the planet's orbits travel) and because the Earth exhibits parallelism (currently toward Polaris, the North Star) as it revolves about the Sun.

At the extreme of the solar system, Pluto, usually the most distant planet (i.e., at certain times Neptune's orbit actually extends farther than Pluto's orbit) takes approximately 247 Earth years (the time it takes the Earth to revolve about the Sun) to complete one orbital revolution about the Sun.

Rotation, revolution, polar tilt, parallelism, and Earth's oblate spheroid shape combine to produce an unequal distribution of solar energy, the changing of seasons, the changing lengths of day and night, and influence the circulation of the atmosphere and oceans.

In addition to Earth's rotation about the Sun, the solar system is both moving with the Milky Way galaxy and revolving around the galactic core.

Remebering Nine Planet Names

Remembering which order the planets come in can be difficult, so why not teach your class the following tricks? You could also ask the children to try to make up their own!

(all lists should be read downwards)

Mercury	My	Many	My	Mother
Venus	Very	Very	Vicious	Veronica
Earth	Educated	Elderly	Earthworm	Enjoyed
Mars	Mother	Men	Might	My
Jupiter	Just	Just	Just	Jam
Saturn	Served	Snooze	Swallow	Sandwich
Uranus	Us	Under	Us	Under
Neptune	Nachos / Noodles	Newspapers	Now	Neptune
Contributed by:	Ahmet Kilinc	Rebecca Draper	Joel Schwartz	Annie and Becky

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The International Astronomical Union have voted to change the status of Pluto. The lists at the bottom of this page are therefore no longer correct. However, they are still valuable ways of remembering the order of the planets... just remember that Pluto is now classed as a "dwarf planet".

Mercury	Make	My	My	My	My
Venus	Very	Very	Very	Very	Very
Earth	Easy	Educated / Excellent	Eager	Easy	Easy
Mars	Mash	Mother	Mother	Method	Method
Jupiter	Just	Just	Just	Just	Just
Saturn	Squash	Served / Sent	Served / Sent	Speeds	Simply
Uranus	Up	Us	Us	Up	Uses
Neptune	New	Nine	Nine	Naming	Nine
Pluto	Potatoes	Pies	Pizzas	Planets	Planets
Mercury	Mum's / My	My	Mother	Mary	My
Venus	Very	Very	Very	Very	Very
Earth	Early	Energetic	Easily	Easily	Energetic
Mars	Morning	Mate	Made	Makes	Mother
Jupiter	Jam	Just	Jane	Jam	Just
Saturn	Sandwiches	Swam	Stop	So	Swept
Uranus	Usually	Under	Using	You	Up
Neptune	Nauseate	North	Nail	Needn't	Nine
Pluto	People	Pier	Polish	Panic	Pins
Mercury	My	My	My	My	Mrs
Venus	Very	Very	Very	Very	Van
Earth	Evil	Easy	Excited / Educated	Energetic	Eats
Mars	Mother's	Method	Mother	Mother	Mainly
Jupiter	Jokes	Just	Just	Just	Jam
Saturn	Sometimes	Shows	Showed	Spent	Strawberry
Uranus	Upsets	Us	Us	Under	Usually
Neptune	Nervous	Nine	Nine	Nine	Never
Pluto	People	Planets	Planets	Pounds	Plum
Mercury	Many	My	Many	My	My
Venus	Vile	Very	Very	Very	Very
Earth	Earthlings	Expensive	Early	Early	Enormous
Mars	Make	Monkey	Mammals	Marrows	Monster
Jupiter	Jam	Jumps	Journeyed	Just	Just
Saturn	Sandwiches	Softly	South	Suited	Sucked
Uranus	Under	Under	Unto	Uncle	Up
Neptune	Newspaper	Neath	New	Ned	Nine
Pluto	Piles!	Pluto	Pastures	Perfectly	Planets