Page 28 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

How do

stromatolites

Could these odd rock structures
form? be the earliest signs of life?

hey might not look like much, but trapped in the layers along with grains of
stromatolites are the oldest fossils to be sediment. These layers would slowly build up on
Tfound on Earth. They are essentially top of one another, with the bacteria migrating
layered mounds of sediment and calcium upwards through the sediment to remain on the
carbonate that build up around colonies of top level.
single-celled organisms like cyanobacteria, a A well-developed stromatolite mound is likely
photosynthesising microbe which can still to represent at least 10,000 years of growth and
be found today. will often contain a myriad of shapes depending
When fully formed they resemble boulders, on the environment in which it grew. It’s
but they are actually composed of layer upon believed that the continued formation of
layer of material accumulated by the stromatolites aided the creation of a breathable
cyanobacteria, trapped by the mucus they atmosphere, due to the vast quantities of oxygen
produce naturally. As these bacteria produced by the photosynthetic bacteria. This

photosynthesised they used up carbon dioxide underlies their significance; human life may not
in the surrounding water, causing calcium have been possible if these tiny organisms had
carbonate to precipitate out and also become not come into existence.

What’s behind California’s

unique climate? From moist sea air to dry desert, find out about

North California’s climate zones
Great Basin
Coastal mountains By the time air reaches the
As sea air rises over the coastal mountains it California’s desert region
Moist sea air expands and cools, which may result in its moisture levels have
Prevailing winds in the condensation followed by rainfall, if enough been depleted, causing it to
area blow moist air in moisture is present. sink and become even
from the Pacifi c Ocean, drier. Incredibly hot
from west to east. temperatures have been
recorded here, including an
astounding reading of 57°C
(134°F) in 1913.

Groundwater flow Central Valley Sierra Nevada
Both stream run-off and The sea air sinks down once it passes the As air is forced to rise over the high mountains of the
groundwater flow carry dissolved coastal mountains, becoming drier. Sierra Nevada region, it undergoes further cooling

salts back to the ocean, Following this, it regains some of its moisture which usually results in more rainfall, or snow in the
contributing to the ocean’s salt through evaporation and plant transpiration. winter. This mountain range is approximately 110km © Thinkstock
concentration. Evaporation is also These two processes occasionally result in the (70mi) wide and has a significant impact on

a factor in ocean salinity. formation of fog. California’s climate.
28 How It Works