I am so thankful God is full of Grace and Mercy. He has had to hear of our sins and destruction since the beginning. One day like a flash of lightening He will send Jesus to come and rescue His followers. I look at the news each day like today where many have died a tortuous death in Syria from chemical weapons and history has been very ugly to His planet and all that is on and in it ,century after century. No one knows when He will say enough. When I saw how many volcanoes are ready to erupt right now darkness came to mind. It will dark when Jesus returns maybe a darkness as Pharaoh had to feel during Moses. There is one Volcano they are watching Mount Hekla called Gateway to Hell. There will be no doubt when He returns.
Matthew 24
26“Therefore if they say to you, ‘Look, He is in the desert!’ do not go out; or ‘Look, He is in the inner rooms!’ do not believe it. 27For as the lightning comes from the east and flashes to the west, so also will the coming of the Son of Man be.

Volcanoes in the past have darkened parts of the planet in the past like 6th century darkened Europe's skies.
[link to phys.org (secure)]

God shows us with Pharaoh how great His patience is and gives many warnings. We know from Scriptures He will show that same Mercy up to the last hour.
Matthew 24
29“Immediately after the tribulation of those days the sun will be darkened, and the moon will not give its light; the stars will fall from heaven, and the powers of the heavens will be shaken. 30 Then the sign of the Son of Man will appear in heaven, and then all the tribes of the earth will mourn, and they will see the Son of Man coming on the clouds of heaven with power and great glory. 31And He will send His angels with a great sound of a trumpet, and they will gather together His elect from the four winds, from one end of heaven to the other.
So do not let your heart grow faint God has been and is in control of all elements. Scriptures tells us what will happen , warnings and mercy being shown at the same time. Ephesians 4:9 (Now that he ascended, what is it but that he also descended first into the lower parts of the earth? I only have to remember my walks in Yellowstone and the smells to be reminded what is in the lower parts of earth.
Prepare our Hearts O Lord.