There's tons of information here.. this is taken from the section
called "The Elder Edda"... it explains the world-ash (the tree)
MaTa
Cosmology
In 'The Song of the Sybil' it is said that in the beginning there was
nothing but a 'yawning gap'. The Sybil herself, however,
says that she knows of nine worlds, and Vafthrudnir the giant claims
that he has seen nine worlds. The poetry refers to the
gods' construction of Midgard, and the raising of the temple in
Asgard. The term Midgard (Middle World) implies to Snorri a
tricentric structure of the universe with Asgard in the center,
Midgard about it, and Utgard (Outer World) as the third ring.
Utgard, we must assume further, contains Jötunheim (Land of the
Giants), Alfheim (Land of the Elves), Svartalfheim (Land of
the Dark Elves), and perhaps Vanaheim (Land of the Vanes). Somewhere
below this structure is Nifiheim, the realm of the
goddess Hel. The ninth world may be that of the dwarves, but its
proper name and its specific location are uncertain. Asgard,
the world of the gods, and Midgard, the world of man, are protected
from Utgard by a large body of water in which swims
the Midgard-Serpent, so huge that he encircles all Midgard and clasps
his tail in his mouth. Asgard and Midgard are
connected to each other by a bridge Bifröst (Rainbow) which is said
to span the water. It is across this bridge that the
enemies of the gods will fare at Ragnarök. The world-ash Yggdrasil
has one of its three roots embedded in Asgard, the
second in Utgard, and the third in Nifiheim. Under the first root is
the spring of Urd (Future, or Fate; Old English Wyrd,
Shakespeare's weird as in the weird sisters of Macbeth), under the
second is the well of Mimir, Odin's source of wisdom,
and under the third is the spring Hvergelmir, source of all rivers.
The dragon Nidhögg (Deep-Biter) gnaws at the deepest
root, and above four dwarves (North, South, East and West) support
the sky. Two wolves pursue the sun and moon, and
will catch and swallow them at Ragnarök.
Utgard must be a completely mountainous and cold region. Frost
giants, mountain giants and rock elves live there. Jötunheim
must be northward from Asgard, since the north is traditionally the
land of death and the land of man's enemies. The trolls,
presumably, live in the east or northeast, for Thor is frequently
described as being 'in the east, fighting trolls'. Hel is also
somewhat to the north as well as downward, since Snorri's
Gylfaginning tells how Hérmod rode after Baldur to Hel, 'deep
and to the north'. To the south lies Muspellheim (the Realm of Fire).
It is difficult to say how much the Icelandic concept of
Hel was influenced by the mountainous and volcanic character of
Iceland, but the dimension of depth is suggested elsewhere
in poetic descriptions. In 'The Lay of Grimnir' Odin looks out over
the world from his throne, or high seat, Hlidskjálf (Hall of
Many Doors). Frey sees down into Jötunheim from Hlidskjálf in
'Skirnir's Ride'. Whether Odin or any occupant of Hlidskjálf
can see over the world just because the seat is high, or because
Odin's home has certain magic properties is uncertain. As we
are told that the occupant of Hhdskj álf can 'see out over all the
worlds', we have placed Asgard on the edge of the universe,
rather than in the center (where Snorri seems to place it, cf. pp.164
and 172).
The dramatic situation in each of the mythological poems involves a
movement between worlds, and often suggests descents
from one plane to another. In 'The Song of the Sybil' Odin has
journeyed downward to Nifiheim to charm the Sybil into
speech. 'The Lay of Vafthruthnir' is a quest into Jötunheim not only
to test the giant's wit, but to learn of the impending fate of
the gods. 'The Lay of Grimnir 'is ostensibly a quest to test human
virtue, but it turns into an exposition of Odin's wit, as well as
a revelation of his pseudonyms. 'Skirnir's Ride' is Frey's quest for
a bride in Jötunheim, and Thor quests for a giant kettle in
'The Lay of Hymir' in which to brew beer for the gods' feast. 'The
Lay of Thrym' is a quest to recover from Jötunheim Thor's
hammer. 'Baldur's Dreams' is another of Odin's quests to learn of the
fate of the gods. 'Brunhild's Hel-Ride' tells of Brunhild's
journey from Midgard to Hel as the Valkyrie seeks to follow her slain
lover Sigurd (in Hel rather than in Valhalla because he
was slain in bed rather than on the battlefield).
Descent into a lower world in order to acquire secrets of life and
death denied living beings is a mythological archetype. Odin
parallels heroes of many traditions in this respect - Gilgamesh,
Ulysses, Aeneas, and Sir Guyon are but a few. Odin wins his
battle of wits in such confrontations with knowers of truth, but
generally fails to grasp the significance of the answers he
extracts. Not until he questions the Sybil does he receive the full
and explicit statement of the gods' fate.
The mythological poems of Icelandic tradition are typo-logically
related to Nordic heroic legends in poetry. The former
constitute a kind of mythological explication of the condition of
universal life, and the latter illustrate struggles of men within
these conditions. What happens in Asgard foreshadows what will come
to pass in Midgard. As the gods struggle to prevent a
destruction they know is inescapable, so heroes are implicitly urged
to face inevitable fate without succumbing to despair. As
the race of gods anticipates resurrection, so the heroes anticipate
enduring fame. The typo-logical association between poems
of gods and poems of heroes lends them similar structures. The lays
of Thrym and Völund illustrate this general
correspondence. Each hero, Völund and Thor, is robbed of his most
valued p05session, without which each feels powerless.
To regain his hammer, Thor must allow himself to be disguised as a
woman; Völund, before he can regain his sword, is
hamstrung. Each must journey to another world before recovering his
loss, and, in each instance, recovery takes place during
a kind of mock wedding. Völund weds Bodvild (whom he calls his
'bride') by assaulting her. Thor's wedding feast ends with
his slaughter of the giants. Both tales echo earlier myths of
regeneration.
Despite the frequent journeys of gods to Jötunheim and to Midgard,
there is very little mingling of the affairs of mortals with
the affairs of gods. For the most part, gods are conspicuously absent
in the heroic poems, and mortals are absent from the
poems about gods (except for references to men in the prose
accompanying the poems). Giants never appear in Midgard,
and when dwarves appear they seem to refer more to stunted humans
than to the enemies of gods. Although Valhalla is an
important concept in heroic life, there are no poems, other than the
contrived 'Lay of Erik', that mention the presence of
mortals in Asgard.