What percentage of the ocean has been explored in detail by humans?
AnswerLess than a quarter
Only around 20 to 25% of the seafloor is mapped at high resolution (Seabed 2030).
Outdoors · Facts & stats
Open Water facts & stats
7 fact-checked facts about oceans, lakes and the open water we share, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
What causes tides?
AnswerThe Moon's and Sun's gravity
Lunar gravity is the main driver, with the Sun adding spring and neap tide cycles.
Going deeper
About how much of the oxygen we breathe comes from the ocean?
AnswerRoughly half
Phytoplankton produce an estimated 50% or more of the world's oxygen.
What is ocean acidification?
AnswerFalling seawater pH as it absorbs CO₂
The ocean has absorbed about 30% of human CO₂, lowering pH by about 0.1 since pre-industrial times, which harms shell-builders.
Mangroves protect coasts and also...
AnswerStore large amounts of carbon in their soils
Mangroves, seagrass and salt marshes are 'blue carbon' ecosystems that store carbon for centuries.
Expert level
How much plastic is estimated to enter the ocean each year?
AnswerRoughly 8 to 11 million tonnes
Jambeck et al. (2015) estimated 8 million tonnes a year; later studies put it around 11 million.
What is a marine heatwave?
AnswerA period of unusually warm sea surface temperatures lasting days to months
Marine heatwaves have doubled in frequency since the 1980s and drive mass coral and kelp die-offs.
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