"When he opened the seventh seal, there was silence in heaven for about half an hour." NIV translation
When the Lamb that is Jesus opened the final seal on the scroll, there was a pause where everything stopped and became quiet. In chapter six, the seals were opened and terrible things happened to the earth. Normally, when bad things happen there are many people who run to God for help and that probably happened with the opening of the previous six seals. Usually, many of these people will then turn away from God when things get better because they never really came to God in faith and repentance. When things calm down, they go back to their old ways. This pause, with the opening of the final seal, is a time of calm when many will think that they don't need God anymore. God is slow to anger and does not take pleasure in judgment but this pause is also a transition from the time of grace to God's judgment.
"And I saw the seven angels who stand before God, and to them were given seven trumpets." NIV translation
Once again, we must remember that the number seven represents spiritual completeness. God used trumpets in the Old Testament to communicate with His people. On the way to the promised land (a picture of heaven), God told Moses to make two silver trumpets to communicate with His people (see Numbers 10). The trumpets were used to call the Israelites to assemble at the Tent of Meeting. When a single trumpet was sounded, the princes (leaders) of the tribes were to assemble and, when two trumpets were sounded, all of the people were to assemble. The trumpets were also blown during times of war so that God's people would be saved from the enemy. The trumpets were also blown over the sacrifices on days of gladness and solemn days. As we can see from these Old Testament uses of the trumpet, they were for calling God's people and not for warning the enemies of God. That is what is going to happen here as God calls His people to Him and those that are left will face the judgment.
"Another angel, who had a golden censer, came and stood at the altar. He was given much incense to offer, with the prayers of all the saints, on the golden altar before the throne." NIV translation
The golden altar is the place of prayer and the prayers of the saints were mixed with the smoke of burning incense.
Revelation 8:4 & 5
"The smoke of the incense, together with the prayers of the saints, went up before God from the angel's hand. 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." NIV translation
The incense was mixed with the prayers of the martyrs (those that had died for their faith).
We saw, in chapter six, that when the fifth seal of the scroll was opened it revealed these martyrs praying for judgment to come to the earth. In this passage, God answers their prayers when the censer of fire is thrown down to the earth.
Thunder is a warning of an approaching storm and so the earth reacts to the coming judgment. The rumblings that are mentioned is actually voices so that those on earth know it is not simply a storm coming but it is of God. Lightning is another sign of a storm getting close and finally the earth reacts with an earthquake.
"Then the seven angels who had the seven trumpets prepared to sound them." NIV translation
Why would the angels have to prepare to sound them? God has not been waiting with joy at the thought of judging the earth and everything in it but He must give the order. The angels are standing by and you can almost feel the sadness at the expectation of what is to come.
"The first angel sounded his trumpet, and there came hail and fire mixed with blood, and it was hurled down upon the earth. A third of the earth was burned up, a third of the trees were burned up, and all the green grass was burned up." NIV translation
The first trumpet has been sounded and the plants of the earth are affected. In Genesis, plants were the first living things to be created on the earth. Without plants, it is not possible for animals or people to live and so the judgment begins with them as well. This is similar to the plague of hail that God sent to Egypt to deliver His people (see Exodus 9:22-26).
Revelation 8:8 & 9
"The second angel sounded his trumpet, and something like a huge mountain, all ablaze, was thrown into the sea. A third of the sea turned into blood, a third of the living creatures in the sea died, and a third of the ships were destroyed." NIV translation
There is a small but key word in this passage that is often missed and that is the word "like". Many people say that a mountain must be thrown into the sea but that is not what it says. A huge fiery mass, like a mountain, is going to be hurled down from the heavens and land in the sea. This could possibly be a meteor. One third of the sea turning to blood reminds us of the plague of blood in Exodus chapter seven. This will kill one third of the creatures in the sea and one third of the ships will be destroyed when it lands in the sea.
Revelation 8:10 & 11
"The third angel sounded his trumpet, and a great star, blazing like a torch, fell from the sky on a third of the rivers and on the springs of water - the name of the star is Wormwood. A third of the waters turned bitter, and many people died from the waters that had become bitter." NIV translation
This passage reminds us of Moses and the bitter waters in Exodus 15:22 -25. In Exodus, God turned the bitter waters of Marah into sweet water by using a piece of wood which is a picture of Jesus' payment for sin on the wooden cross. After the water was changed from bitter to sweet, God promised that he would not bring plagues on His people if they follow the leading of the Lord. Now, in this passage from Revelation, the people have abandoned following God and the waters are being turned from sweet waters of life to bitter waters of death. God uses a star to do this so that people will know that it is a divine judgment and not simply the effects from pollution which are so widespread today.
"The fourth angel sounded his trumpet, and a third of the sun was struck, a third of the moon, and a third of the stars, so that a third of them turned dark. A third of the day was without light, and also a third of the night." NIV translation
In Genesis 1, we are told that God created the sun, moon, and stars to provide light to the earth. Here we see that God has started to turn out the lights because the party is over. This is just a preview of what it will be like for those who will spend eternity in hell as God is light and so without Him there is complete darkness.
"As I watched, I heard an eagle that was flying in midair call out in a loud voice: 'Woe! Woe! Woe to the inhabitants of the earth, because of the trumpet blasts about to be sounded by the other three angels!'" NIV translation
When an eagle speaks, I would think that you need to listen. An eagle represents speed and this eagle is warning the people of the earth that they have not seen anything yet (as far as judgment) and that the next three blasts are coming quickly. Although there were people that died in the first trumpet blasts, now the judgment is going to turn directly to the people of the earth. These are the three woes that are to come and they deal directly with the people.