Sunday, May 24, 2009
Alan V. Morgan
Thursday,
February
12th,
2009.
Surely
today
has
some
significance?
My
computer
countdown
clock
chimed
to
inform
me
that
it
had.
I
was
up
early,
on
a
not
so
sunny
day
at
Sani
Lodge
in
the
tribal
lands
of
the
Yasuni
on
the
Napo
River,
one
of
the
major
tributaries
of
the
Amazon.
The
day
was
important
because
exactly
200
years
earlier,
Charles
Darwin
had
been
born
in
Shrewsbury,
England,
setting
events
in
motion
some
22
years
later
which
would
resonate
through
various
fields
of
science
to
the
present.
I
refer
to
Darwin’s
voyage
on
H.M.S.
Beagle,
a
ten
gun
brig
that
sailed
from
Devonport,
Plymouth,
in
southwestern
England
on
the
27th
of
December,
1831.
As
I
mentioned
in
an
earlier
issue
of
Wat
On
Earth
(see:
Winter
2006)
Darwin’s
travels
and
interests
have
crossed
with
my
own
in
many
places
in
various
parts
of
the
world.
However,
this
was
my
first
visit
to
South
America
where
Darwin
spent
the
bulk
of
his
time
as
a
“part-time
gentleman”
companion
with
Captain
Fitzroy
and
for
the
next
two
months
was
able
to
cross
many
different
parts
of
his
route.
I
thought
I
would
bring
his
observations
and
my
own
together
in
this
article.
Of
course
Darwin
never
got
into
the
headwaters
of
the
Amazon,
and
probably
the
closest
he
came
to
the
region
was
when
the
Beagle
made
landfall
in
the
Galapagos
Islands
some
1,500
km
to
the
west.
Nevertheless,
his
travels
in
Brazil,
Argentina
and
Chile
must
have
first
introduced
him
to
the
vast
diversity
of
tropical
life
and
also
set
the
stage
for
his
observations
and
thoughts
that
radically
changed
biological
concepts
over
20
years
later
in
1859.
In
order
to
follow
“in
the
footsteps”
I
have
commented
on
some
selected
localities
visited
by
Darwin
in
the
period
from
1832
to
1834.
Many
of
these
are
quite
distant
from
each
other
and
not
necessarily
in
the
order
that
Darwin
visited
them.
Darwin’s
first
lengthy
stay
in
South
America
was
in
Brazil
and
he
spent
some
time
at
Botofogo
(currently
Botafogo)
Bay
in
what
is
now
part
of
Rio
de
Janeiro.
His
residence
was
quite
close
to
the
near
vertical
mountain,
Corcovado,
about
4
km
from
both
the
renowned
Sugarloaf
and
from
Ipanema
Beach.
Our
visit
to
Rio
was
short,
but
like
most
visitors
I
was
truly
impressed
by
the
startling
topography
around
the
city,
much
of
which
has
also
been
enhanced
by
the
recent
drowning
of
the
coastline.
In
the
Journal
of
Researches
Darwin
had
commented:
Everyone has heard of the beauty of the scenery near Botofogo. The house in which I lived was seated close beneath the well-known mountain of the Corcovado. It has been remarked, with much truth, that abruptly conical hills are characteristic of the formation which Humboldt designates as gneiss granite. Nothing can be more striking than these huge rounded masses of naked rock rising out of the most luxuriant vegetation.
Sugarloaf
at
396
m,
Corcovado
at
710m
and
the
many
and
varied
monolithic
hills
of
Rio
are
wonderful
examples
of
inselbergs.
These
are
residual
hills
derived
from
the
tropical
weathering
of
feldspathic
granite
plutons
of
late
Precambrian
age(about
570
million
years
old).Chemical
weathering
and
“spalling”—
the
exfoliation
of
surficial
layers
of
rock,
have
helped
to
produce
the
steep
to
near-vertical
sides
seen
on
the
hills.
Similar
features
can
be
seen
in
Yosemite
Park;
for
example
“Half
Dome”,
and
just
north
of
Vancouver
near
Squamish,
the
“Stawamus
Chief”
although
both
North
American
examples
have
been
modified
by
glacial
activity
and
this
is
not
true
of
the
Brazilian
peaks.
After
reaching
the
top
of
Sugarloaf
(some
fairly
obvious
feldspathic
dykes
easily
seen
in
the
approach
to
the
summit
station)
we
returned
to
the
middle
station
on
Urca
Mountain.
Here
workers
had
been
blasting
and
a
number
of
fresh
exposures
illustrated
the
large
feldspar
phenocrysts
present
in
the
granite.
We
then
walked
down
the
southern
side
where
we
saw
some
really
excellent
palled
slabs
that
had
moved
away
from
the
exposed
rock
surfaces
and
had
settled
onto
the
coastal
pathway.
Our
journey
then
took
us
south
to
the
estuary
of
the
River
Plate
and
the
cities
of
Buenos
Aires
in
Argentina
and
Montevideo
in
Uruguay.
It
was
in
this
area
that
Darwin
had
first
found
fossils
of
Quaternary
age,
some
of
which
were
new
to
science.
His
fossil
mammal
finds
his
visit
to
the
Falkland
Islands
and
some
additional
observations
in
South
America
will
be
described
in
separate
articles.
Eventually
all
sailors
travelling
westward
around
South
America
either
have
to
pass
around
the
infamous
Cape
Horn,
or
through
either
the
Straits
of
Magellan
or
the
Beagle
Channel.
Both
of
these
short
cuts
eliminate
the
potentially
stormy
passage
around
the
Cape.
We
were
fortunate
in
rounding
the
Horn
in
relatively
calm
seas
eastbound,
but
were
prevented
by
very
stormy
weather
from
doing
so
westbound.
Cape
Horn,
perhaps
unknown
by
many,
is
not
part
of
the
South
American
mainland.
It
is
actually
the
southernmost
promontory
on
Isla
Hornos,
part
of
the
Hermite
Islands
south
of
Tierra
del
Fuego
(which
in
itself
is
also
another
large
island
south
of
South
America).
Without
being
able
to
go
ashore
it
was
difficult
to
make
out
much
of
the
geology
of
Cape
Horn
even
through
a
400mm
lens,
but
it
did
appear
that
north
of
the
Horn
predominantly
light
coloured
rocks
(perhaps
metamorphic
or
igneous)
are
penetrated
by
dykes
of
what
appear
to
be,
basalt
or
andesites.
(See
inside
cover).
Travelling
westward
our
next
encounter
with
Darwin
and
his
Beagle
voyage
was
in
the
Beagle
Channel.
His
comments
are
worth
recording
because
of
the
implications
of
global
warming.
January
29th
1833:
Early in the morning we arrived at the point where the Beagle Channel divides into two arms; and we entered the northern one. The scenery here becomes even grander than before. The lofty mountains on the north side compose the granitic axis, or backbone of the country, and boldly rise to a height of between three and four thousand feet, with one peak above 6,000 feet. They are covered by a wide mantle of perpetual snow, and numerous cascades pour their waters, through the woods, into the narrow channel below. In many parts, magnificent glaciers extend from the mountain side to the water’s edge. It is scarcely possible to imagine anything more beautiful than the beryl-like blue of these glaciers, and especially as contrasted with the dead white of the upper expanse of snow. The fragments which had fallen from the glacier into the water were floating away, and the channel with its icebergs presented, for the space of a mile, a miniature likeness of the Polar Sea.
Many
people
travelling
through
these
southern
Chilean
fjords
have
expressed
admiration
for
the
intensely
blue-coloured
ice
of
the
many
glaciers
that
lie
perched
on
the
slopes
above
the
Beagle
Channel.
Even
Darwin
commented
on
the
“Berylblue”
of
the
glaciers.
The
blue-
ranging
to
turquoise-coloured
ice
often
present
in
glaciers
is
due
to
reflectance
of
light.
Red
and
yellow
wavelengths
are
more
easily
absorbed
by
ice
crystals
than
blue.
When
glacial
ice
has
lots
of
bubbles
in
it,
it
tends
to
scatter
all
incoming
visible
wavelengths
and
so
the
ice
appears
grey
or
white.
Any
Earth
scientist
traversing
this
region
cannot
help
noting
the
large
expanses
of
bare
bedrock
surrounding
various
glacier
and
ice
field
margins.
These
have
to
be
ascribed
to
“modern”
glacial
retreat.
It
appears
that
the
maximum
recent
extent
of
glacial
ice
in
several
parts
of
southern
Chile
was
about
1860,
some
30
years
after
Darwin’s
voyage,
and
since
then
glacier
margins
have
been
rapidly
retreating.
Our
journey
west
along
the
Beagle
Channel,
a
deep
glacial
fjord,
followed
Darwin’s
route
to
the
southwestern
coast
of
Chile.
It
was
here
that
he
experienced
(but
did
not
recognize)
the
forces
that
manifest
themselves
in
Plate
Tectonics.
Like
Darwin
and
many
other
sailors
in
this
region
we
encountered
several
major
storms,
and
one
could
really
empathise
with
Darwin
who
survived
a
similar
gale.
In
January
1833
he
wrote:
“… On the 13th the storm raged with its full fury; our horizon was narrowly limited by the sheets of spray borne by the wind. The sea looked ominous, like a dreary waving plain with patches of drifting snow; whilst the ship laboured heavily, the albatross glided with its expanded wings right up the wind. At noon a great sea broke over us, and filled one of the whale boats, which was obliged to be instantly cut away. The poor Beagle trembled at the shock, and for a few minutes would not obey her helm; but soon, like a good ship that she was, she righted and came up to the wind again. Had another sea followed the first our fate would have been decided soon, and forever.” (… and although he did not know it, the course of science likely would have been changed, at least until Wallace’s ideas on evolution were expressed)!
Of
course
there
was
a
vast
difference
in
the
size
of
our
two
vessels.
The
poor
Beagle
was
27.5
m
long
and
7.5
m
wide
and
weighed
242
tons.
The
Star
Princess
is
290
m
long,
36
m
wide
and
weighs
109,000
tons!
(The
Beagle
would
have
fitted
into
the
central
pool
area
of
the
Star
Princess)!
Nevertheless
viewing
the
storm
from
the
top
deck,
about
150
feet
above
the
sea
was
quite
impressive!
Our
journey
continued
northward
along
the
coastline
of
Chile,
where
we
had
the
opportunity
to
sail
between
Chiloe,
the
fifth
largest
island
in
South
America
and
the
mainland
coast
of
Chile.
Darwin
sailed
the
same
route
in
the
Beagle
arriving
in
Chiloe
on
November
10th
,
1834.
It
was
here
that
Darwin
had
the
opportunity
of
seeing
three
regional
volcanoes
in
simultaneous
activity.
One
of
these
(Osorno)
is
shown
on
p.14,
but
the
2300m
Corcovado
volcano
(not
to
be
confused
with
the
peak
in
Rio
de
Janeiro)
and
the
2404m
Minchinmávida
were
also
active.
All
three
volcanoes
produce
basaltic
to
andesitic
lavas.
In
the
same
area
the
1122
m
Chaiten
caldera
was
in
eruption
while
we
were
passing,
but
unfortunately
we
were
too
far
away
to
observe
the
eruption
cloud.
Chaiten
is
an
unusual
acidic
volcano
that
is
extruding
rhyolitic
lavas
and
translucent
grey
obsidian
that
in
former
times
was
used
by
the
prehistoric
people
of
the
region.
Darwin
finally
reached
Valparaiso
on
July
23,
1834,
and
his
travels
to
the
north
will
be
concluded
in
other
summaries
in
Wat
On
Earth.