Table of contents | |
Water Cycle | |
Distribution of Water Bodies | |
Ocean Circulation | |
1. Waves | |
2. Tides | |
3. Ocean Currents |
Water is all around us, from the flowing streams in forests to the raindrops that tap on our windows. Have you ever wondered where all this water comes from and where it goes? Water is an essential resource that covers about three-fourths of the Earth’s surface, existing in various forms such as rivers, lakes, oceans, glaciers, and even water vapor in the atmosphere. Despite its abundance, only a small percentage of water is available as freshwater suitable for human use.
The water cycle is a continuous process where water changes its form and circulates between the oceans, atmosphere, and land. Here’s how it works:
Water cycle
Our planet works like a giant terrarium, where the same water has been cycling for centuries. The water that waters crops today might have traveled down the Amazon River a hundred years ago. This cycle is crucial for sustaining life on Earth as it distributes water across different regions.
Note: A terrarium is a miniature, enclosed ecosystem designed to mimic a natural environment. You can create your own by filling a jar with soil and plants and closing it. The water that evaporates from the leaves and soil will condense and fall back, just like in the water cycle.Terrarium
Freshwater mainly comes from rivers, ponds, springs, and glaciers. However, the water in oceans and seas is salty. Oceans have a lot of dissolved salts, mostly sodium chloride, which is the same as the salt you use in your food.
Sources | Percentage |
Oceans | 97.3 % |
Ice-caps | 2 % |
Ground Water | 0.68 % |
Freshwater lakes | 0.009 % |
Inland seas and salt lakes | 0.009 % |
Atmosphere | 0.0019 % |
Rivers | 0.0001 % |
Important Fact:
About two billion people worldwide don’t have access to safe drinking water today (SDG Report 2022), and roughly half of the world’s population is experiencing severe water scarcity for at least part of the year (IPCC). These numbers are expected to increase, exacerbated by climate change and population growth (WMO).
Walking barefoot on the seashore feels like magic. The wet sand, the cool breeze, the seabirds, the salty smell, and the sound of the waves are all amazing. Unlike ponds and lakes, the ocean water is always in motion. It never stays still. The movements in the ocean can be divided into waves, tides, and currents.
The movements that occur in oceans are of three types
Important Fact:
The term "tsunami" is a Japanese word that means "harbour waves," as harbors often get destroyed during these events.
Ocean Waves
Tides are the rise and fall of ocean water that occurs twice a day.
- High tide covers much of the shore.
- Low tide occurs when the water recedes.
Neap and Spring Tides
Significance of Tides:
Ocean currents are continuous flows of seawater that move across the ocean's surface in specific directions, similar to rivers within the sea.
Warm and Cold ocean currents
Warm and Cold Ocean Currents:
Impact of Ocean Currents:
66 videos|336 docs|46 tests
|
1. What are the main types of ocean circulation? |
2. How do waves form in the ocean? |
3. What causes tides in the ocean? |
4. What are ocean currents and why are they important? |
5. How do ocean currents affect weather and climate? |
|
Explore Courses for Class 7 exam
|