Grade 8 Science: Water Systems on Earth

Grade 8 Science: Unit 1 - Water Systems on Earth

• This unit explores the Earth's water systems and their effects.
• Images of the Churchill River, a large ocean wave, and interactive questions concerning water use are included.
• A diagram of water distribution on Earth quantifies the different forms of water (freshwater, saltwater, ground water, etc.)
• Only 3% of Earth's water is freshwater (no salt).
• Two-thirds of freshwater is frozen in ice sheets.
• Only 1% of Earth's freshwater can be used.
• Lithosphere: solid rocky ground of Earth's crust
• Atmosphere: environment surrounding Earth
• Hydrosphere: all water on Earth, including within the lithosphere and atmosphere
• The water cycle is a constant process where water cycles through evaporation and condensation, changing form between gas and liquid. Evaporation and condensation are driven by the sun's energy.
• 80% of total water vapor comes from the ocean.

Water Differences

• Salinity: the amount of salt dissolved in a specific amount of water. Salt comes from dissolved solids in the ground and volcanoes.
• Fresh water: contains tiny amounts of salt
• Saltwater: average salinity of 35 parts per thousand (ppt) which is variable depending on location.
• Density: the amount of mass of a substance in a certain unit volume;. How tightly packed a material is in a substance.
• Ocean water is more dense than fresh water because of its higher salt content.
• Freezing Point: the temperature at which a liquid freezes
  • Fresh water freezes at 0°C
  • Saltwater freezes at -1.9°C

Sources of Freshwater

• Lakes, ponds, wetlands
• Streams, rivers
• Ground water
• Glaciers
• Drainage basins (areas of land that drain into a body of water)
• A divide separates one basin from another; an example is the Continental Divide.
• Runoff does not sink into the ground or evaporate; it flows across the Earth's surface. Factors affecting runoff include ground material, rainfall, rainfall duration, land slope, vegetation, and development.

Glaciers

• A glacier is a moving mass of snow and ice.
• Glaciers form in areas where the snow remains year-round.
• Glaciers can be found in mountains and on continents, such as Antarctica.
• Glaciers slow down the water cycle by storing vast quantities of water, and release water during warmer months.
• Glaciers are useful in providing scientists with data on Earth's past climate.

The Ice Age

• The most recent ice age began 120,000 years ago and ended 11,000 years ago.
• Glaciers covered roughly 20% of the Earth's land

Glaciers and Global Warming

• In the past 100 years, global average surface temperatures have risen by 0.5°C.
• The world's glaciers are melting at an accelerated pace.
• Rising ocean waters may lead to flooding of rivers if glaciers disappear.

Core Lab Activities

• Unit 1 contains two core lab activities: Salinity's Effect on Water Density and Temperature & Water Density.

Canadian Drainage Basins

• Major drainage areas in Canada include the Arctic Western and Northern Hudson Bay, Maritime Provinces, Great Slave Lake, Northern Quebec and Labrador, Pacific, St. Lawrence, Mississippi River, Nelson River, Yukon River, and Southwestern Hudson Bay.
• Six major drainage basins in Newfoundland and Labrador are the Labrador Sea, Gulf of St. Lawrence, West Coast, South Coast, Atlantic Ocean Avalon Peninsula, and Atlantic Ocean Northeast Coast.

General Considerations

• One component (ex. Salinity or temperature) affects another (ex. types of organisms or dissolved oxygen).
• Convergence of currents (ex. Labrador and Gulf Stream currents) affects important things in the environment.