The answer is both.
Satan can cause natural disasters if he has God’s permission. Satan caused the disasters that came on Job:
“Then the LORD said to Satan, “Have you considered my servant Job? There is no one on earth like him; he is blameless and upright, a man who fears God and shuns evil.”
“Does Job fear God for nothing?” Satan replied. “Have you not put a hedge around him and his household and everything he has? You have blessed the work of his hands, so that his flocks and herds are spread throughout the land. But stretch out your hand and strike everything he has, and he will surely curse you to your face.”
The LORD said to Satan, “Very well, then, everything he has is in your hands, but on the man himself do not lay a finger.”
Then Satan went out from the presence of the LORD.
One day when Job’s sons and daughters were feasting and drinking wine at the oldest brother’s house, a messenger came to Job and said, “The oxen were plowing and the donkeys were grazing nearby, and the Sabeans attacked and carried them off. They put the servants to the sword, and I am the only one who has escaped to tell you!”
While he was still speaking, another messenger came and said, “The fire of God fell from the sky and burned up the sheep and the servants, and I am the only one who has escaped to tell you!”
While he was still speaking, another messenger came and said, “The Chaldeans formed three raiding parties and swept down on your camels and carried them off. They put the servants to the sword, and I am the only one who has escaped to tell you!”
While he was still speaking, yet another messenger came and said, “Your sons and daughters were feasting and drinking wine at the oldest brother’s house, when suddenly a mighty wind swept in from the desert and struck the four corners of the house. It collapsed on them and they are dead, and I am the only one who has escaped to tell you!” Job 1:8-19
“Then the LORD said to Satan, “Have you considered my servant Job? There is no one on earth like him; he is blameless and upright, a man who fears God and shuns evil. And he still maintains his integrity, though you incited me against him to ruin him without any reason.”
“Skin for skin!” Satan replied. “A man will give all he has for his own life. But stretch out your hand and strike his flesh and bones, and he will surely curse you to your face.”
The LORD said to Satan, “Very well, then, he is in your hands; but you must spare his life.”
So Satan went out from the presence of the LORD and afflicted Job with painful sores from the soles of his feet to the top of his head. Then Job took a piece of broken pottery and scraped himself with it as he sat among the ashes.” Job 2:3-8
God causes disasters. For instance, He punished Sodom and Gomorrah for their sin:
“The two men said to Lot, “Do you have anyone else here—sons-in-law, sons or daughters, or anyone else in the city who belongs to you? Get them out of here, because we are going to destroy this place. The outcry to the LORD against its people is so great that he has sent us to destroy it.” Genesis 19:12-13
Children of God have power through prayer to avert disaster. In the case of Sodom and Gomorrah, Abraham’s prayer would have changed God’s mind if the conditions were met:
“Then he said, “May the Lord not be angry, but let me speak just once more. What if only ten can be found there?”
He answered, “For the sake of ten, I will not destroy it.” Genesis 18:32
Ten righteous men were not found in the city.
Abraham’s prayer did save the lives of his righteous nephew Lot and his family:
“So when God destroyed the cities of the plain, he remembered Abraham, and he brought Lot out of the catastrophe that overthrew the cities where Lot had lived.” Genesis 19:29
“and if he rescued Lot, a righteous man, who was distressed by the filthy lives of lawless men.” 2 Peter 2:7
A friend told how her church had prayed when a tornado was coming their way. The tornado bypassed the church though the church was in the tornado’s path. God hears our prayers in disasters, although sometimes He chooses not to have us escape them entirely. Our prayers have an important influence on what happens, and the amount of influence might surprise us.
God also inflicted plagues on Egypt:
“The elders of Israel will listen to you. Then you and the elders are to go to the king of Egypt and say to him, ‘The LORD, the God of the Hebrews, has met with us. Let us take a three-day journey into the desert to offer sacrifices to the LORD our God.’ But I know that the king of Egypt will not let you go unless a mighty hand compels him. So I will stretch out my hand and strike the Egyptians with all the wonders that I will perform among them. After that, he will let you go.” Exodus 3:18-20
God is in control. He explains that He chose Pharaoh purposely—Pharaoh’s disobedience would bring God glory:
“It does not, therefore, depend on man’s desire or effort, but on God’s mercy. For the Scripture says to Pharaoh: “I raised you up for this very purpose, that I might display my power in you and that my name might be proclaimed in all the earth.” Therefore God has mercy on whom he wants to have mercy, and he hardens whom he wants to harden.” Romans 9:16-18
The book of Jonah gives some interesting insight into God’s control of nature and His character. He used a vine to protect His servant and later destroyed the vine to discipline him and show Jonah His great compassion for the wicked who repent:
“But the LORD said, “You have been concerned about this vine, though you did not tend it or make it grow. It sprang up overnight and died overnight. But Nineveh has more than a hundred and twenty thousand people who cannot tell their right hand from their left, and many cattle as well. Should I not be concerned about that great city?” Jonah 4:10-11
A few more examples include the earthquake when Jesus died:
“When the centurion and those with him who were guarding Jesus saw the earthquake and all that had happened, they were terrified, and exclaimed, “Surely he was the Son of God!”” Matthew 27:54
The earthquake when the angel moved the stone away from Jesus’ grave:
“There was a violent earthquake, for an angel of the Lord came down from heaven and, going to the tomb, rolled back the stone and sat on it.” Matthew 28:2
And the earthquake that freed Paul and Silas from prison:
“Suddenly there was such a violent earthquake that the foundations of the prison were shaken. At once all the prison doors flew open, and everybody’s chains came loose.” Acts 16:26
In the book of Revelation the earthquakes that will come are to show God’s glory and give man a chance to repent:
“I watched as he opened the sixth seal. There was a great earthquake. The sun turned black like sackcloth made of goat hair, the whole moon turned blood red,” Revelation 6:12
“Then the angel took the censer, filled it with fire from the altar, and hurled it on the earth; and there came peals of thunder, rumblings, flashes of lightning and an earthquake.” Revelation 8:5
“At that very hour there was a severe earthquake and a tenth of the city collapsed. Seven thousand people were killed in the earthquake, and the survivors were terrified and gave glory to the God of heaven.” Revelation 11:13
“Then God’s temple in heaven was opened, and within his temple was seen the ark of his covenant. And there came flashes of lightning, rumblings, peals of thunder, an earthquake and a great hailstorm.” Revelation 11:19
“Then there came flashes of lightning, rumblings, peals of thunder and a severe earthquake. No earthquake like it has ever occurred since man has been on earth, so tremendous was the quake.” Revelation 16:18
Most of the time disasters are the result of natural laws God has put in place. In the following instance Jesus seems to have meant that if they did not repent, they would die as the natural consequence of a fallen world:
“Now there were some present at that time who told Jesus about the Galileans whose blood Pilate had mixed with their sacrifices. Jesus answered, “Do you think that these Galileans were worse sinners than all the other Galileans because they suffered this way? I tell you, no! But unless you repent, you too will all perish. Or those eighteen who died when the tower in Siloam fell on them—do you think they were more guilty than all the others living in Jerusalem? I tell you, no! But unless you repent, you too will all perish.” Luke 13:1-5
Either the storm in the following passage was planned by God the Father or He took advantage of natural happenings to glorify Himself:
“Immediately Jesus made the disciples get into the boat and go on ahead of him to the other side, while he dismissed the crowd. After he had dismissed them, he went up on a mountainside by himself to pray. When evening came, he was there alone, but the boat was already a considerable distance from land, buffeted by the waves because the wind was against it.
During the fourth watch of the night Jesus went out to them, walking on the lake. When the disciples saw him walking on the lake, they were terrified. “It’s a ghost,” they said, and cried out in fear.
But Jesus immediately said to them: “Take courage! It is I. Don’t be afraid.”
“Lord, if it’s you,” Peter replied, “tell me to come to you on the water.”
“Come,” he said.
Then Peter got down out of the boat, walked on the water and came toward Jesus. But when he saw the wind, he was afraid and, beginning to sink, cried out, “Lord, save me!”
Immediately Jesus reached out his hand and caught him. “You of little faith,” he said, “why did you doubt?”
And when they climbed into the boat, the wind died down. Then those who were in the boat worshiped him, saying, “Truly you are the Son of God.” Matthew 14:22-33
Following is another example of God being glorified either through a natural consequence or a planned event:
“That day when evening came, he said to his disciples, “Let us go over to the other side.” Leaving the crowd behind, they took him along, just as he was, in the boat. There were also other boats with him. A furious squall came up, and the waves broke over the boat, so that it was nearly swamped. Jesus was in the stern, sleeping on a cushion. The disciples woke him and said to him, “Teacher, don’t you care if we drown?”
He got up, rebuked the wind and said to the waves, “Quiet! Be still!” Then the wind died down and it was completely calm.
He said to his disciples, “Why are you so afraid? Do you still have no faith?”
They were terrified and asked each other, “Who is this? Even the wind and the waves obey him!” Mark 4:35-41
The natural laws that cause “disasters” are themselves the consequence of Adam’s sin:
“For the creation was subjected to frustration, not by its own choice, but by the will of the one who subjected it, in hope that the creation itself will be liberated from its bondage to decay and brought into the glorious freedom of the children of God. We know that the whole creation has been groaning as in the pains of childbirth right up to the present time.” Romans 8:20-22
Notice that disaster caused by Satan is against the righteous, while disaster caused by God is against wickedness. Whether Satan causes the disaster, the disaster is a consequence of natural laws or God directly causes the disaster—no matter what the reason—God is totally in control and will be glorified by what happens.
The two great disasters of ancient times were brought on by man’s sin. In both cases, the righteous were rescued from them. Before Jesus sets up His kingdom, the worst disaster of all will come on the world. The Bible speaks often about God’s final wrath:
“Therefore wait for me,” declares the LORD, “for the day I will stand up to testify. I have decided to assemble the nations, to gather the kingdoms and to pour out my wrath on them— all my fierce anger. The whole world will be consumed by the fire of my jealous anger.” Zephaniah 3:8
"The angel swung his sickle on the earth, gathered its grapes and threw them into the great winepress of God’s wrath.” Revelation 14:19
The righteous (those who believe in Jesus) will be rescued to receive an everlasting reward. The Bible even tells how they will be rescued:
“For the Lord himself will come down from heaven, with a loud command, with the voice of the archangel and with the trumpet call of God, and the dead in Christ will rise first. 17 After that, we who are still alive and are left will be caught up together with them in the clouds to meet the Lord in the air. And so we will be with the Lord forever.” 1 Thessalonians 4:16-17
“For God did not appoint us to suffer wrath but to receive salvation through our Lord Jesus Christ.” 1 thessalonians 5:9
The final disaster is likened to the disaster in the days of Noah and Lot:
“No one knows about that day or hour, not even the angels in heaven, nor the Son, but only the Father. As it was in the days of Noah, so it will be at the coming of the Son of Man. For in the days before the flood, people were eating and drinking, marrying and giving in marriage, up to the day Noah entered the ark; and they knew nothing about what would happen until the flood came and took them all away. That is how it will be at the coming of the Son of Man. Two men will be in the field; one will be taken and the other left. Two women will be grinding with a hand mill; one will be taken and the other left.” Matthew 36-41
“Just as it was in the days of Noah, so also will it be in the days of the Son of Man. People were eating, drinking, marrying and being given in marriage up to the day Noah entered the ark. Then the flood came and destroyed them all.
“It was the same in the days of Lot. People were eating and drinking, buying and selling, planting and building. But the day Lot left Sodom, fire and sulfur rained down from heaven and destroyed them all.” Luke 17:26-29
The heavens and earth will be destroyed by fire, and God will make new a new heavens and earth unscarred by sin:
“But the day of the Lord will come like a thief. The heavens will disappear with a roar; the elements will be destroyed by fire, and the earth and everything in it will be laid bare.
Since everything will be destroyed in this way, what kind of people ought you to be? You ought to live holy and godly lives as you look forward to the day of God and speed its coming. That day will bring about the destruction of the heavens by fire, and the elements will melt in the heat. But in keeping with his promise we are looking forward to a new heaven and a new earth, the home of righteousness.” 2 Peter 3:9-13
Finally, the world will understand the consequences of sin. The wicked who follow Satan will suffer forever, and the righteous who follow Jesus will share in His glory forever:
“If anyone’s name was not found written in the book of life, he was thrown into the lake of fire.” Revelation 20:25
“For God so loved the world that he gave his one and only Son,[a] that whoever believes in him shall not perish but have eternal life.” John 3:16