Grade 8 Science: Water Systems on Earth

Grade 8 Science: Unit 1 - Water Systems on Earth

• This unit explores Earth's water systems
• Topics covered include water's effects, distribution, the water cycle, differences between ocean and fresh water, sources of fresh water, and the impact of glaciers and global warming.

Effects of Water

• Images of the Churchill River and large ocean waves illustrate water's impact.
• Water use categorized by uses: Household, Personal, and Recreational (as buttons on a screen).

Water Distribution

• Only 3% of Earth's water is fresh water.
• Two-thirds of fresh water is frozen in ice sheets.
• Only 1% of the Earth's fresh water is readily available.
• Earth's water broken down: Saline (oceans) 97%, Fresh water 3%.
• Fresh water further broken down into: Ground water 30.1%, Ice caps & Glaciers 68.7%, Surface water 0.3%, Rivers 2%, Lakes 87%, Swamps 11% , Other 0.9%.
• This detailed breakdown of water distribution illustrates the relative abundance of different types of water on Earth.

The Water Cycle

• Water constantly cycles between liquid, gas (vapor), and solid (ice) forms.
• Evaporation from the ocean contributes about 80% of the water vapor in the atmosphere
• Precipitation, runoff, groundwater, and cloud formation are key aspects of the water cycle.
• The sun's energy drives the water cycle.

Ocean Water vs. Fresh Water

• Salinity: The amount of salt dissolved in a specific amount of water.

  • Ocean water salinity is about 35 parts per thousand (ppt), and varies by location.
  • Fresh water has tiny amounts of salt

• Density: The amount of mass of a substance in a volume.

  • Ocean water is more dense than fresh water.

• Freezing point: Water freezes at 0°C (fresh water) and -1.9°C (sea water)

Sources of Fresh Water

• Lakes, ponds, and wetlands
• Streams and rivers.
• Groundwater: Precipitation that sinks into the ground and collects in rock pores
  • Wells can be drilled to reach groundwater.
• Glaciers: Moving masses of snow and ice (mostly from snowy areas), found in cold areas.
• Drainage basins: Areas of land that drain water into a particular body of water.

Glaciers

• Glaciers are moving masses of snow and ice.
• They are found in areas with persistent cold, snow accumulates year-round.
• Glaciers store a large amount of water for the water cycle (slowing it down), and are released during warmer periods.
• They provide information on past climates.
• The images show current glacier melt from past glacier photos.

The Ice Age

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

Glaciers and Global Warming

• Average global temperatures have risen by 0.5°C over the last 100 years.
• Glaciers are now melting at a faster rate than in the past.

Drainage Basins

• Drainage basins are areas of land that drains water into a body of water such as a river, pond, lake, or ocean.
• Divides separate one drainage basin from another (e.g., The Continental Divide).
• Canada has multiple drainage basins

One Component Affects Another

• Factors like salinity and temperature influence the types of organisms that can survive in a particular area.

  • Salinity affects ocean life whereas temperature affects oxygen dissolved in water

• Convergence of currents (e.g., Labrador and Gulf Stream) affects productivity, icebergs formation, and animal migration.

Explore Earth's water systems in this quiz focused on Unit 1. Topics include the water cycle, distribution of fresh and saline water, and the impact of glaciers and global warming. Understand the critical roles water plays in our environment and daily life.