The Doctrine and Covenants, Section 88:94-98

94 And another angel shall sound his trump, saying: That great church, the mother of abominations, that made all nations drink of the wine of the wrath of her fornication, that persecuteth the saints of God, that shed their blood–she who sitteth upon many waters, and upon the islands of the sea–behold, she is the tares of the earth; she is bound in bundles; her bands are made strong, no man can loose them; therefore, she is ready to be burned. And he shall sound his trump both long and loud, and all nations shall hear it.

95 And there shall be silence in heaven for the space of half an hour; and immediately after shall the curtain of heaven be unfolded, as a scroll is unfolded after it is rolled up, and the face of the Lord shall be unveiled;

96 And the saints that are upon the earth, who are alive, shall be quickened and be caught up to meet him.

97 And they who have slept in their graves shall come forth, for their graves shall be opened; and they also shall be caught up to meet him in the midst of the pillar of heaven–

98 They are Christ’s, the first fruits, they who shall descend with him first, and they who are on the earth and in their graves, who are first caught up to meet him; and all this by the voice of the sounding of the trump of the angel of God.

Journal of Discourses, Orson Pratt 8:10

After all nations have heard the proclamation, there will be silence in the heavens, and I do not know but on the earth too; for the people will doubtless be overpowered with astonishment to see an angel, the sound of whose trump shall pierce the ears of all living. After this, I say, there will be silence in heaven for half-an-hour.