Geology Reference
In-Depth Information
Stromatolites
are mounded structures built by colonies of algae as they grow
upward toward the sun. Stromatolites form when tiny strands of algae trap
particles of sand and other sediments between them (see Figure 18-4A). As the al-
gae die, they form layers of sediment from the trapped particles (see Figure
18-4B). New algae grows on top of them, up toward the sunlight (see Figure 18-4C).
Over time a mound of sediment and algae layers forms (see Figure 18-4D). You can
see a fossil stromatolite in this topic's color photo section.
Figure 18-3:
The
biological process
of photo-synthesis.
Figure 18-4:
Form-
ation of a stro-
matolite as algae
strands trap sedi-
ments.
