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Oceans & Seas

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Facts about the world's oceans and seas.

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Question

What percentage of Earth's surface is covered by ocean?

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1What percentage of Earth's surface is covered by ocean?
Approximately 70.8% (361 million km²)
2What is the largest ocean by area?
Pacific Ocean (168,723,000 km², 46.6% of total ocean area)
3What is the average depth of Earth's oceans?
3,688 meters (12,100 feet)
4What percentage of Earth's water is contained in the oceans?
97% of Earth's water (and 97.5% of total water volume)
5What is the deepest point in the ocean?
Challenger Deep in the Mariana Trench (10,971 meters / 35,994 feet)
6What are the five major oceans of Earth?
Pacific, Atlantic, Indian, Antarctic/Southern, and Arctic oceans
7What is the second largest ocean?
Atlantic Ocean (85,133,000 km², 23.5% of total ocean area)
8What is the volume of the Pacific Ocean as a percentage of all oceans?
50.1% (669,880,000 km³)
9Which ocean is sometimes considered a marginal sea of the Atlantic?
Arctic Ocean (15,558,000 km², 1.4% of ocean volume)
10What is the Indian Ocean's area?
70,560,000 km² (19.5% of total ocean area)
11Between which continents does the Pacific Ocean lie?
Between Asia and Australia, and the Americas
12What percentage of Earth's atmospheric oxygen does the ocean produce?
Half of it (photosynthesis in the ocean supplies 50% of Earth's oxygen)
13What is the average depth of the Arctic Ocean?
1,205 meters, making it the shallowest major ocean
14What is the photic zone in the ocean?
The depth at which light intensity is only 1% of the surface value, approximately 200 m in the open ocean, where photosynthesis can occur
15What is the average temperature of the world ocean?
3.9°C, because most ocean water is in the deep, cold layers
16What is the maximum surface temperature in tropical oceans?
Over 30°C (86°F)
17What is the ocean temperature near the poles where sea ice forms?
About -2°C (28°F)
18What is the origin of the word 'ocean'?
From Oceanus (Ōkeanós), a Titan in Greek mythology who personified an enormous river encircling the world
19What is the difference between an ocean and a sea?
A sea is a body of water partly or fully enclosed by land, while oceans are the large, open divisions of the world ocean
20When was Lake Superior's water formed?
Evidence suggests water existed on Earth 3.8 billion years ago based on pillow basalt from the Isua Greenstone Belt
21What is the longest mountain range in the world?
The global mid-oceanic ridge system (65,000 km / 40,000 mi), underwater
22What percentage of the ocean floor has been mapped at high resolution as of 2024?
Just over 26%, with some estimates suggesting only 5% has been explored
23What is Point Nemo?
The oceanic pole of inaccessibility in the South Pacific, roughly 2,688 km from the nearest land
24What is the combined volume of water in all oceans?
Roughly 1.335 billion cubic kilometers (320.3 million cubic miles)
25What is the average salinity of Earth's oceans?
About 35 grams of salt per kilogram of seawater (3.5%)
26Why is ocean water blue?
Water preferentially absorbs red light while blue light is reflected; water molecules and tiny particles also scatter blue light more than other colors
27How deep can blue light penetrate in the ocean?
Up to 200 meters (656 ft), while red light is absorbed within 50 meters (164 ft)
28What is a thermocline?
A distinct boundary between warmer surface water and colder deep water, where temperature changes dramatically with depth
29What are the pelagic zones divided by light penetration?
Photic zone (light for photosynthesis), mesopelagic/twilight zone (very little light), and aphotic zone (no sunlight)
30What is the mesopelagic zone?
The twilight zone where there is very small amount of light, between the photic zone and aphotic deep ocean