There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
martalmar
place name. Roots of the Earth
talmar ambaren
place name. Roots of the Earth
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
The “veins of the world” in some cosmological notes from the 1930s (SM/241-2, 255), also appearing in The Etymologies as combination of mar “world” and the plural of talma “root” (Ety/TAL).