The following are my “favorite” plausible end of world scenarios posted in a Guardian article by science correspondent, Alok Jha. To add to the “Gamma Rays From Space” scenario, our sun also emits gamma rays during solar flares; a big enough solar flare would do the trick as supposed to waiting for a nearby star to go supernova.
MEGA TSUNAMI
Geologists worry that a future volcanic eruption at La Palma in the Canary Islands might dislodge a chunk of rock twice the volume of the Isle of Man into the Atlantic Ocean, triggering waves a kilometre high that would move at the speed of a jumbo jet with catastrophic effects for the shores of the US, Europe, South America and Africa.
Danger sign: Half the world’s major cities are under water. All at once.
GEOMAGNETIC REVERSAL
The Earth’s magnetic field provides a shield against harmful radiation from our sun that could rip through DNA and overload the world’s electrical systems. Every so often, Earth’s north and south poles switch positions and, during the transition, the magnetic field will weaken or disappear for many years. The last known transition happened almost 780,000 years ago and it is likely to happen again.
Danger sign: Electronics stop working.
GAMMA RAYS FROM SPACE
When a super-massive star is in its dying moments, it shoots out two beams of high-energy gamma rays into space. If these were to hit Earth, the immense energy would tear apart the atmosphere’s air molecules and disintegrate the protective ozone layer.
Danger sign: The sky turns brown and all life on the surface slowly dies.
RUNAWAY BLACK HOLE
Black holes are the most powerful gravitational objects in the universe, capable of tearing Earth into its constituent atoms. Even within a billion miles, a black hole could knock Earth out of the solar system, leaving our planet wandering through deep space without a source of energy.
Danger sign: Increased asteroid activity; the seasons get really extreme.