Yes, rocks do tell stories! Earth is made
of rock. Thousands of different types of rocks and
minerals have been found on Earth. Most rocks at
the surface (where humans can see) are formed from
only eight elements (oxygen, silicon, aluminum,
iron, magnesium, calcium, potassium, and sodium),
and these elements are combined in a variety of
ways to form very different rocks. Each rock
tells its own story, and those stories in
combination record the history of Earth.
Earth's surface is constantly changing:
mountains are built, rivers cut canyons, wind and
water carry rock and deposit it in new locations,
flat layers became folded and faulted, and hot,
molten rock from below Earth's surface seeps out
as lava. Earth is over 4.5 billion years
old, and most of that history has been
destroyed by erosion, burial, and modification
from heat and compression at depth. However, some
fragments remain, like the Acasta gneiss from
Canada (dated to about 4 billion years, this is
the oldest known rock on Earth) and the Jack Hills
zircon from Australia (dated to 4.4 billion years
old, these are the oldest known minerals on
Earth). By studying how rocks form and how
they become new rocks, scientists have developed a
good understanding of how Earth formed and how it
has changed through time.
Since Earth is made up of rock, no one
"discovered" a first rock. In fact, it is
challenging to know who the first person to think
critically about rocks might have been. Like all
science, the study of Earth has evolved with
technology and human understanding. Generally,
the first advanced thoughts around Earth
(including mineralogy, cartography, geography, and
geology) are attributed to ancient Greece.
The oldest known maps are preserved on 2300 B.C.
Babylonian clay tablets. Xanthus of Lydia
(modern day Turkey) and Herodotus of ancient
Greece were historians who occasionally wrote
about geology and the natural world during the 5th
century B.C. (500-400 B.C.).
The concept of a spherical Earth was widely
accepted in Greece around 350 B.C.. Strabos of
Greece wrote a book titled, "Geography" before 24
A.D. Pliny the Elder of Rome wrote one of the
earliest encyclopedic works on natural and
geographic phenomena shortly before his death in
79 A.D. Modern geology is attributed to James
Hutton from Edinburgh, who dedicated himself
to the study of rocks beginning in 1768. He laid
the foundation for scientific geology.
There are many various types of rocks and many can
tell fascinating stories about the way they
formed. Some rocks will only have minerals
that can form at very high pressures, so we know
that the rock needed to form deep in the earth or
in a place where an asteroid struck. Some rocks
have fossils in covered in mudstone, rock which
formed from mud under the pressure of rocks above
it. Those can tell us stories about the place
where the animal died.
People have known and used rocks for a long
time, even before people called themselves
scientists. One of the first minerals that was
discovered a bit more recently was
magnetite, a magnetic mineral that was used
for the first compasses. We do not know the exact
person that discovered the mineral, but many
ancient civilizations knew about it and used it to
navigate in the ocean.
Rocks contain information about how the rock was
formed, and what forces the rock was subjected to
before we found it. By looking at many rocks,
we can construct a story about the history of the
Our ancestors have known about rocks since long
before our ancestors were human beings. Ancient
peoples certainly knew that different kinds of
rocks were useful for different things, such as
different building materials, or containing
different kinds of ores for smelting. The first
person credited for looking at rocks as records of
the past is often Leonardo da Vinci, but even
he probably wasn't the first (he was also largely
Rocks tell lots of stories. They tell whether
they formed from sediments that got pressed
together under water, or from volcanic eruptions.
Some of them tell about ancient plants and
animals that lived when the rocks were being
formed. Scientists can tell how old the rocks
are, because the rocks have different ratios of
isotopes of elements such as oxygen, depending on
when they were formed.
What do you think about scientists and
rocks? When do you think rocks were first
discovered? How old do you think you were when
you first discovered a rock?
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