Appendix A: Background Information For First-Time Teachers

Backgrounder #1: Global climatic determiners and Saskatchewan's climate

Solar radiation reaching the earth may be reflected by clouds, or pass through the atmosphere, either heating the air or reaching the earth's surface. There, longer wavelengths may be absorbed, warming the land or water surface, or reflected (and possibly being trapped by "greenhouse gases", warming the atmosphere.) Visible wavelengths may be absorbed by vegetation and some of the energy converted from light to chemical form-- carbohydrates-- in photosynthesis, effectively trapping a portion of the solar energy as producer biomass and forming the foundation of the food chains that sustain biotic communities.

The curvature of the earth's surface affects the intensity of solar radiation per unit of area, with intensity decreasing toward the poles. As well, the thickness of the atmosphere through which the solar radiation passes is greater as the angle increases, further reducing the amount of energy reaching the surface. Finally, permanent ice caps and seasonal snow cover reflect more energy back into space, further reducing heating. Result: the surface receives progressively less heat (and light) energy toward the poles.

The slope of the earth's axis causes significant annual differences, outside tropical regions, in the amount of heat and light reaching the surface as the earth moves around the sun. Result: seasons.

All of this is complicated by the presence of oceans and continents that heat and cool differently. Land tends to cool at night and get warmer during the day, while ocean temperatures fluctuate little. Furthermore, outside tropical regions day length varies significantly with the seasons, further complicating annual regional climatic patterns.

Finally, ocean currents and continental topographic features such as mountain ranges, mean elevation and inland water bodies, contribute further variability to climate patterns.

The net effect of all these global factors for Saskatchewan gives most of the province a continental climate, with most weather coming from the northwest or southwest:

• prevailing winds blow from the west and northwest for most of the year (south and east in spring only), with the potential in winter for Arctic air masses over the northern part of the continent to generate cold north winds
• moist air from the North Pacific Ocean flowing over Western Canada in an easterly direction loses much of its water as rain and snow on the Coast Ranges and the Rocky Mountains. Average annual precipitation in Saskatchewan ranges from 55cm in the northeast to less than 30 cm in the far southwest, of which about 30% falls and remains as snow, making effective precipitation zero for over half the year. This snow melts in a short time period, creating significant seasonal surface water and runoff during the spring months. Much of this moisture enters the soil, but a significant amount may be lost due to frozen subsurface soil, rapid run-off and high evaporation as daytime temperatures rise, relative humidity decreases and prevailing winds carry the moist air away
• average annual temperature varies from slightly above freezing to well below freezing, decreasing toward the north. The period of time when nighttime temperatures do not regularly drop below freezing (frost-free period) lasts from about 70 to 100 days annually, making for a relatively short growing season. Long cold winters freeze the soil and surface water to depths well below a metre (much deeper in years of sparse snowfall) and trap precipitation as snow, creating conditions of low relative humidity that allows extreme fluctuations between daytime and nighttime temperatures in winter. Even summertime daily temperature fluctuations are large, due to the low heat-holding capacity of relatively dry air.

Outline of a sample exercise for analyzing a local climate:

Climatic Factors And Their Effects

From information provided by your teacher, construct a standard climograph for (location) and answer the following questions based on it:

• What is the average annual temperature?
• During which months is the average monthly temperature above this annual average?
• How well does this period coincide with the period deciduous trees are in leaf?
• Why are the average monthly temperatures a misleading indicator of plant activity?

The average date for last spring frost in this location is ***; for first fall frost it is ***.

• How many days does this average frost-free period encompass?
• How does this period compare with the leaf season?
• What percentage of the year does the frost-free period represent?
• Is the growing season identical for all wild plants in the environment? Give evidence from your own experience and explain.
• What is the total annual precipitation for this location?
• What is the average monthly precipitation?
• During which months is the precipitation above average?
• What percentage of the annual precipitation falls during this period?
• How well does this period coincide with the leaf season?
• Winter precipitation is effective as moisture only when it melts. During how many months is the effective precipitation therefore zero?
• What is the total precipitation "stored up" during this period?
• What percentage of annual precipitation is this?
• During which month(s) is it released? Using a different colour, sketch this "released moisture" on your climograph.
• When winter precipitation is released by melting, it is not all available to the living community. What happens to the rest of it? Why?
• Which parts of the local environment will be most affected by this relatively rapid release of moisture? In what ways?
• Based on your answers to the previous questions, summarize in a paragraph the ways in which climate influences the nature of the local environment.

Backgrounder #2: How climatic factors influence global vegetation patterns-- and the Saskatchewan vegetation zones that result

The dominant vegetation of a region is largely determined by climate. Outside polar and subpolar regions, progressively lower annual precipitation (or longer dry seasons) gives rise to different major plant types:

• high year-round precipitation supports permanently green rainforests
• moderate to high annual precipitation interrupted by an annual dry season supports deciduous forests, which conserve moisture during dry seasons by losing their leaves
• lower annual precipitation (with or without a dry season) favours grasslands (prairie), whose vegetation, dying back to ground level annually, can survive with less moisture or a shorter growing season than can trees
• sparse or infrequent precipitation results in deserts, whose vegetation is adapted to dry air and low soil moisture.

In the circumpolar northern latitudes from around 54 degrees N, precipitation is relatively low (although ranging from desert-like to levels comparable to moist grasslands). Vegetation types in this region are significantly influenced by annual temperature pattern as well as annual precipitation:

• very short summers and soil permanently frozen (permafrost) below a few centimetres favours tundra vegetation consisting of simple plants such as lichens and seed plants that have small waxy evaporation-resistant leaves, minimal annual growth and a short reproduction cycle
• slightly longer summers, in regions without widespread permafrost near the surface, support boreal forests that consist predominantly of slow-growing evergreen trees adapted to low moisture conditions by having extensive shallow root systems and waxy needle-like leaves that are not shed in the fall and whose active growing season can be thus extended until the soil freezes.

Within Saskatchewan there are two major vegetation regions: boreal forest and grassland. The northern boreal forest, in which evergreen conifers predominate, occupies approximately the northern 40% of the province, while on its southern fringe a broad band of mixed forest (the southern boreal forest), averaging perhaps 150 km wide, extends from northwest to southeast. The boundary between forest and open grassland is quite gradual, with aspen parkland occupying a transition zone averaging perhaps a further 100 km and forested patches appearing well south of that as well. With the parkland included, grassland or prairie occupies approximately the southern third of the province, extending farther north on the west and beginning farther south near the Manitoba border. Within each of these larger regions, differences in soil, residual moisture, elevation and latitude produce local variations in vegetation pattern and associated wildlife.

Backgrounder #3: Some fundamental concepts in historical geology

1. Evidence from absolute dating (the measurement of time by studying the rate of decay of radioactive elements in rock) indicates that the earth is very old (in the range of 4.6 billion years) and parts of the earth's crust, while perhaps a billion years younger, are very old as well.
2. Changes in the earth's crust and the earth's surface are believed to have occurred gradually, over very long periods of time, by processes we can observe in the present day (Principle of Uniformitarianism).
3. The most common of these processes are weathering (breaking down of rock through physical and chemical processes such as frost, gravity and the chemical and physical actions of plant roots) and erosion (transport of the products of weathering, most commonly through the action of water falling as rain and running from land to sea.)
4. Other major erosional forces include ice, particularly in the form of continental ice sheets and wind.
5. The oldest rocks are a result of molten material that solidified as the earth's crust cooled early in the planet's life; regions of the earth's land surface composed of these rocks are sometimes referred to as shields.
6. The layers (strata) of rock that make up much of the upper crust of the earth's land masses were formed from sediments deposited in water as a result of weathering of older rocks.
7. In undisturbed strata, any layer (stratum) of rock is older than the stratum on top of it and younger than the stratum beneath it (Principle of Superposition).
8. The layers of sediment may contain recognizable remains or other evidence (fossils), or transformed products (e.g., coal, petroleum, natural gas) of plants, animals and microorganisms alive at the time the sediments were deposited.
9. The relative age of strata in different locations may be inferred from the kinds of fossil organisms found in them (index fossils; Principle of Faunal Succession).
10. Some of these sediments and their fossil content, have been bound by pressure and physical processes into various kinds of rocks classified as sedimentary.
11. Other sediments and their fossil content, have been transformed by heat and pressure to form various kinds of rocks classified as metamorphic.
12. Any rock that has formed from molten material is classified as igneous; shield rock, therefore, is igneous.
13. Not all igneous rock is old: solidified lava, resulting from recent (or ancient) vulcanism, is also igneous.
14. Portions of the earth's crust show evidence of having changed position over the course of earth history, both laterally (plate tectonics or 'continental drift') and vertically (uplift or compression).
15. In addition to vertical movement of the crust, sea levels have apparently risen and fallen over the course of earth history, sometimes flooding existing land areas for long periods of time and sometimes exposing new land to the forces of weathering and erosion.
16. Portions of the earth's surface beneath the water do not weather appreciably, but may become covered by new strata due to the accumulation of sediments from erosion from the nearby land surfaces; conversely, portions of the earth's surface above sea level do not add new sedimentary strata, but are worn down by weathering and erosion.
17. The boundaries (unconformities) between strata are understood to indicate a time period when no sediments were being deposited in a particular location (or perhaps existing deposits were being worn away.)
18. The major strata of the earth's crust have been studied and compared by geologists and placed in a sequence (youngest at the top, oldest at the bottom) called the Worldwide Geological Column. No single location on earth, however, has been found to contain all of these strata.
19. Some rocks contain significant amounts of particular minerals, which may have formed in igneous rock from molten material from the earth's mantle, or in metamorphic rock by transformation through heat and pressure, or in sedimentary rock by deposition, concentration and transformation through evaporation, compression and chemical activity.
20. Major processes affecting the nature and transformation of the earth's crust tend to be repetitive or cyclic in nature: the rock cycle, the mineral cycle, the hydrologic (water) cycle, the carbon/carbonate cycle.

Backgrounder #4: Some fundamental concepts in physical geography

1. The earth's present land surface (topography) has been shaped over the long term by the movement of crustal plates (plate tectonics/continental drift) and geological uplift (e.g., mountain building) and in the shorter term by the geological processes of erosion and deposition, particularly as a result of periods of continental glaciation.
2. The land surface is in many places covered with soil, a mixture of various-sized mineral particles, living organisms and organic material. Most of the soil mineral residue in temperate regions comprises unconsolidated deposits left behind by the continental glaciations of the past 20 000 years.
3. General global climatic zones are determined by a combination of solar energy, the tilt of the earth's axis and the earth's rotation.
4. Each region of the earth's land surface has long-range patterns of temperature, precipitation, solar radiation and air movement-- climate. Regional climate is influenced by the patterns of atmospheric circulation and ocean currents and the location of land masses and mountain ranges.
5. The combination of topography, climate and soil determines which kinds of plants and associated animals (biota: flora and fauna) can survive in a particular location.
6. Topographic characteristics such as elevation and slope, along with the extent of precipitation and evaporation, determine patterns of surface water (ponds, lakes, streams and rivers).

Backgrounder #5: Some fundamentals of Saskatchewan's geological history

1. The northern half of Saskatchewan is primarily exposed igneous and metamorphic rock from an ancient shield (the Precambrian Shield) that forms much of the northern half of North America. This rock, the oldest of which is estimated at about 3 billion years of age, but interspersed with newer igneous rock due to volcanic activity, has been eroded periodically by water and ice for billions of years. It contains deposits of minerals of kinds and quantities to be economically valuable in the present day, including gold, silver, zinc, copper, iron, uranium and diamond. An ancient (Late Precambrian) plain of exposed sedimentary rock, the Athabasca Formation, lies on top of a portion of the Precambrian Shield in northern Saskatchewan.
2. The Precambrian rock of the southern half of Saskatchewan is overlain by progressively more recent sedimentary strata (less than 500 million years old) in progressively greater depths (up to almost 3000 metres) toward the south, deposited during successive periods of erosion of the northern shield and later, the Rocky Mountains to the west. Within these strata are found economically valuable deposits of petroleum, natural gas, coal, potash, sulfur, sodium chloride and sodium sulfate.
3. The province's topography has been shaped primarily by the most recent of several continental ice sheets (the Laurentide ice sheet), which covered virtually the entire province about 18 000 years ago and retreated beyond the northern boundary by about 7 000 years ago, leaving behind hills, plains, lakes, ponds, drainage channels and the unconsolidated sediments, from a few centimetres to several hundred metres in depth, that form the basis of prairie soils.