End of the world ? I've heard of this.
Thermonuclear war breaks out killing most people in most major cities, leaving scattered groups of people.
A large comet hits the Earth causing the sun to be blocked out and billions die from the blast.
A large asteriods land in one of the oceans and causes a massive tidal wave perhaps 1km high destroying most major cities around the world.
A super volcano goes off blocking out the sun for many months killing much of our plant and animals leading to mass starvation.
The Earth's crust shifts causing massive changes to the world map - and of course killing billions in the process.
The rapture takes place just before the outbreak of ww3, leading the wicked to die in world war 3.
Global warming causes ocean levels to rise 230 ft thanks to complete loss of ice, the oceans die due to oxygen depletion which in turn destroys the ozone layer thanks to hydrogen sulfide gas buildup.
A one world government is established and eveyone gets the mark of the beast on their hand otherwise they are killed. World war breaks out.
The world peaks in oil production and this causes economic growth to stagnate, then once the depletion sets in a massive breakdown in our society happens leading to mass starvation, millions of job losses, resource wars, fuel rationing, govenements control the oil. The roads eventually are emptied due to mass shortages of fuel. The knee-jerk reaction is a massive ramp up of synthetic fuel from coal and shale and extra heavy oil. The low energy return and heavy capital investment leads to a worsening of the crisis and leads to a deep depression due to lack of money for most non-essential things. Renewable energy is no longer viable since they all rely on oil in some way. Then natural gas peaks and delines leading to an even worse scenario thanks to the worlds increasing dependence on gas. Then coal peaks and you get the idea.
Important minerals and metals run out, top soil is lost, fish almost run out, the world runs out of arable land and this causes the poor to die out first.
A black hole comes near the Earth or the Sun and destroys either one.
Methane Clathates are released (2,000 billion tons at least) causing massive global temp rises of 10c and possible asphyxiation of those near large deposits.
Never ceases to amaze me. It's an interesting topic and has been around for centuries.
So far most people are betting there will be a contraction of human population before 2050 thanks to overshoot in the carrying capacity of the Earth. Fossil fuel depletion, fresh water depletion, rare metals depletion, phosphate rock depletion, fish depletion, arable land depletion, top soil depletion, co2 buildup, lack of investment capital (thanks to increased price of commodities due to scarcity).