To better understand the symbolism used in the Book of
Revelation for the Land of Israel and for the Gentiles,
Nations, read this Study:

"I beheld another beast coming up out of the earth"
https://www.brighteon.com/ab684e18-d196-4be5-a0b7-5c70c11e31d2

(In Revelation, "Sea" signifies Gentiles and "Earth" refers to the Land of Israel.)

Revelation 6:
9 And when he had opened the fifth seal, I saw under the
altar the souls of them that were slain for the word of God,
and for the testimony which they held:
10 And they cried with a loud voice, saying, How long, O Lord,
holy and true, dost thou not judge and avenge our blood on them
that dwell on the earth?
11 And white robes were given unto every one of them; and it
was said unto them, that they should rest yet for a little season,
until their fellowservants also and their brethren, that should
be killed as they were, should be fulfilled.

Just after the 5th Seal was opened and the souls of the Martyrs,
slain Prophets and Saints of the early Church cried unto God,
when will you avenge our blood on the inhabitants of the Land of
Israel, they were told to wait a little season, because more
innocent blood would still be shed. Then the Sixth Seal was opened.
The key verse that will make it clear what the sixth seal is about,
is pasted below:

Revelation 6:
15 And the kings of the earth, and the great men, and the rich men,
and the chief captains, and the mighty men, and every bondman, and
every free man, hid themselves in the dens and in the rocks of the
mountains;
16 AND SAID TO THE MOUNTAINS AND ROCKS, FALL ON US, AND HIDE US
from the face of him that sitteth on the throne, and from the
wrath of the Lamb:

Now let's compare Revelation 6 verse 16 to what Jesus said when
they were leading him to be crucified:

Luke 23:
27 And there followed him a great company of people, and of
women, which also bewailed and lamented him.
28 But Jesus turning unto them said, Daughters of Jerusalem,
weep not for me, but weep for yourselves, and for your children.
29 For, behold, the days are coming, in the which they shall
say, Blessed are the barren, and the wombs that never bare,
and the paps which never gave suck.
30 THEN SHALL THEY BEGIN TO SAY TO THE MOUNTAINS, FALL ON US;
AND TO THE HILLS, COVER US.
31 For if they do these things in a green tree, what shall be
done in the dry?

(Jesus quoted Hosea 10:8:... they shall say to the mountains,
Cover us; and to the hills, Fall on us.)

The Sixth Seal was opened when inhabitants of Jerusalem
and of the land of Israel began to say to the "Mountains",
"the Rocks" and the "Hills" to fall on them and to cover
them from God who sits on his Judgment Throne and from the
Wrath of Jesus. After the cry of the Souls of the Martyrs
for God to avenge their innocent blood on the inhabitants
of the Land of Israel, from the throne of God, Judgment
was rendered. The time of Vengeance and Retribution was
declared, the innocent blood of the Prophets, of the Lamb
of God and of his Saints will be required of the wicked
and perverse Generation. By divine and righteous Judgment:
the Temple, the city of Jerusalem, Cities of the Land of
Israel will be destroyed...

Revelation 6:
12 And I beheld when he had opened the sixth seal, and, lo,
there was a great earthquake; and the sun became black as
sackcloth of hair, and the moon became as blood;
13 AND THE STARS OF HEAVEN FELL UNTO THE EARTH, EVEN AS A
FIG TREE CASTETH HER UNTIMELY FIGS, WHEN SHE IS SHAKEN
OF A MIGHTY WIND.
14 AND THE HEAVEN DEPARTED AS A SCROLL WHEN IT IS ROLLED
TOGETHER; and every mountain and island were moved out
of their places.

Isaiah 34 King James Version (KJV)
Come near, ye nations, to hear; and hearken, ye people:
let the earth hear, and all that is therein; the world, and
all things that come forth of it.
2 For the indignation of the Lord is upon all nations, and
his fury upon all their armies: he hath utterly destroyed
them, he hath delivered them to the slaughter.
3 Their slain also shall be cast out, and their stink shall
come up out of their carcases, and the mountains shall be
melted with their blood.
4 AND ALL THE HOST OF HEAVEN SHALL BE DISSOLVED, AND THE
HEAVENS SHALL BE ROLLED TOGETHER AS A SCROLL: AND ALL THEIR
HOST SHALL FALL DOWN, AS THE LEAF FALLETH OFF FROM THE VINE,
AND A FALLING FIG FROM THE FIG TREE.
5 For my sword shall be bathed in heaven: behold, it shall
come down upon Idumea, and upon the people of my curse, to
judgment.
6 The sword of the Lord is filled with blood, it is made
fat with fatness, and with the blood of lambs and goats,
with the fat of the kidneys of rams: for the Lord hath a
sacrifice in Bozrah, and a great slaughter in the land of
Idumea.
7 And the unicorns shall come down with them, and the
bullocks with the bulls; and their land shall be soaked
with blood, and their dust made fat with fatness.
8 For it is the day of the Lord's vengeance, and the
year of recompences for the controversy of Zion.