Overview
This lecture covers how to draw profiles from contour maps, introduces Earth's major spheres (hydrosphere, lithosphere, atmosphere), and explains latitude and longitude for location finding.
Drawing Profiles from Contour Maps
- A profile is a side view of a landscape, contrasted with map view (top-down).
- To draw a profile, use a pencil and scrap paper, marking intersection points and elevations where a line crosses contour lines between two points (e.g., B and C).
- Write down the elevation at each crossing, noting whether the terrain is going uphill or downhill.
- Transfer the marked points onto a grid and connect them smoothly, resembling the shape of actual hills or valleys.
- Avoid common mistakes like misreading elevation direction or not including compass direction.
Earth's Spheres
- The hydrosphere covers about 72% of Earth's surface and consists mostly of salt water in oceans.
- The average ocean depth is about 2 miles (10,000 feet), making deep-sea exploration difficult.
- Lithosphere is the rock layer (crust) on Earth's surface, not extending to the core.
- Atmosphere is the air above Earth, containing oxygen needed for life, extending about 100 miles up, with no hard boundary to space.
Shape of the Earth
- Earth is not a perfect sphere; it's an oblate spheroid with a slight bulge at the equator.
- The bulge is so minor that a small sphere is the best model for Earth in drawings.
Latitude and Longitude
- Latitude lines are flat, parallel to the equator ("lat is flat"), and measure north-south position.
- Longitude lines run up and down, meeting at the poles, and measure east-west position.
- Always specify the compass direction (N, S, E, W) with degrees to avoid ambiguity.
- Latitude and longitude examples: 90°W, 30°S, 43°S, 72°N, 40°W, etc.
- New York State is located at approximately 43°N latitude and 76°W longitude.
Key Terms & Definitions
- Profile — A side view of a landscape.
- Contour Map — A map showing elevation using contour lines.
- Hydrosphere — All water on Earth's surface, mostly oceans.
- Lithosphere — The rocky outer layer of Earth (crust).
- Atmosphere — The layer of gases surrounding Earth.
- Latitude — Horizontal lines measuring distance north or south of the equator.
- Longitude — Vertical lines measuring distance east or west of the Prime Meridian.
- Oblate Spheroid — The slightly flattened shape of Earth.
Action Items / Next Steps
- Practice drawing profiles from contour maps as assigned.
- Review the definitions and differences between Earth's spheres.
- Memorize how to read and write latitude and longitude with compass directions.
- Skip page 9 (minutes/seconds in map reading) as instructed.