Lesson Plan

Freeing the Elwha (Aspect and Soil Moisture)

A mid-summer patch of snow remains at Hurricane Ridge.

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Subject:
Astronomy, Biology: Plants, Earth Science, Physical Science
Duration:
One Class Period
Group Size:
Up to 36
Setting:
classroom
National/State Standards:
Washington State Standards:
Science
EALR 4: 6-8 LS2C, EALR 4: 6-8 LS2D
Reading
EALR 1: Component 1.2
Social Studies
EALR 5: Component 5.2
Writing
EALR 2: Component 2.1

Overview

What role do aspect, slope, sun, snow melt, blackbody absorption and elevation play in soil moisture conditions and why is soil moisture important to the structure of an ecosystem?

Background

This lesson focuses on the role of aspect, slope, seasonal sun availability, snow melt, blackbody absorption, and elevation in soil moisture conditions. Soil moisture is one of the most important factors determining the composition of plant communities and ultimately the ecosystem structure. The amount of snowpack and the amount of time it takes to melt off each summer impacts the growing season and the ability of trees to survive. Where trees can no longer survive, alpine meadows predominate, but soil moisture conditions determine whether they are "wet" or "dry" meadows.

  • Aspect: The direction a slope faces
  • Snowpack: The seasonal accumulation of snow in the winter that is available for melting in the spring and summer.
  • Solstice: Either of two times of the year when the sun is at its greatest distance from the celestial equator. The summer solstice in the Northern Hemisphere occurs about June 21, when the sun is in the zenith at the tropic of Cancer; the winter solstice occurs about December 21, when the sun is over the tropic of Capricorn. The summer solstice is the longest day of the year and the winter solstice is the shortest
  • Equinox: Either of the two corresponding moments of the year when the Sun is directly above the Earth's equator. The vernal equinox occurs on March 20 or 21 and the autumnal equinox on September 22 or 23, marking the beginning of spring and autumn, respectively, in the Northern Hemisphere (and the reverse in the Southern Hemisphere). The days on which an equinox falls have about equal periods of sunlight and darkness.
  • Analemma: A graduated scale in the shape of a figure eight, indicating the sun's declination and the equation of time for every day of the year and usually found on sundials and globes.
  • Blackbody absorption: an ideal black substance that absorbs all and reflects none of the radiant energy falling on it.


Materials

  • Lesson 7- Aspect and Soil Moisture.pptx
  • Metal or Glass Pan
  • Shaved Ice
  • Black rubber stopper or another dark object
  • Freezer and/or refrigerator
  • Electric lamp with hot light bulb (100W preferred)
  • Reflection Journal pages (printable handout)
  • Vocabulary Notes (printable handout)


Procedure

Review the Essential Question.

Introduce the guiding Question.
Students should take a few minutes to respond to the first reflection prompts. Discuss their answers and any questions they've generated.
Hand out the Vocabulary Notes. With this lesson you may want to define the words before presenting the PowerPoint Lesson.

Present the PowerPoint Lesson.
Run Demonstration on blackbody radiation absorption.
Have students use the "sun motion simulator" to illustrate the concepts of aspect and shadows and the impact of latitude on seasonal solar radiation. http://astro.unl.edu/naap/motion3/animations/sunmotions.swf
Hand out the second Reflection Journal Page. Give students time for a final reflection on the lesson.



Additional Resources

http://astro.unl.edu/naap/motion3/animations/sunmotions.swf
Analemma
http://spaceplace.nasa.gov/en/educators/NMP_timekeeping.pdf



Vocabulary

Aspect
Snowpack
Solstice
Equinox
Analemma
Blackbody absorption