Aldergrove Park Glacial Erratic EarthCache
Aldergrove Park Glacial Erratic
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Difficulty:
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I used to frequent this park a lot as a child and teen growing up
in this area. My friends and I used to climb the rock and hang out
when we were bored. We didn't do any of the graffiti though. There
are trails that lead right up to the rock.
A glacial erratic is a piece of rock carried by
glacial ice some distance from the rock outcrop from which it
came.
Geologists identify erratics by studying the composition of rocks
surrounding the position of the erratic and the composition of the
erratic itself. Scientists have determined that erratics pointed to
an ice age in Earth's past.
Geologists have suggested that landslides or rockfalls initially
dropped the rocks on top of glacial ice. The glaciers continued to
move, carrying the rocks with it. When the ice melted, the erratics
were left in their present locations.
Erratics can range in size from pebbles to large boulders. The
largest known Glacial erratic is the "Big Rock" erratic(16,500
tons) near Okotoks, Alberta, Canada. Other examples of glacial
erratics include:
A fern-covered erratic the size of a garage is found on Cougar
Mountain near Seattle. White Rock, British Columbia derives its
name from a sea-side erratic the size of a garage found on the
beach at Semiahmoo Bay, right at the US border with Washington
State. The Foothills Erratics Train is a deposit of rocks of many
sizes. These deposits stretch in a narrow belt for about 600 km
from the Athabasca River Valley in Alberta to southwestern Alberta.
During the most recent North American glaciation, the Wisconsin
glaciation (70,000 to 10,000 years ago), ice sheets extended to
about 45 degrees north latitude. This Wisconsinian glaciation left
widespread impacts on the North American landscape.
Fraser Valley
Ice Age sediments deposited during the Pleistocene Epoch (2
million to 11,000 years ago) underlie gently rolling uplands (15 to
250 m elevation) of the Fraser Valley. Most Ice Age sediments in
the Vancouver area date to the last glaciation, about 25,000 to
11,000 years ago, and in particular to the period of glacier
retreat when areas below 200 m elevation were covered by the
sea.
In Eastern Canada and U.S., the Great Lakes and the Finger
Lakes were carved by ice deepening old valleys. Most of the lakes
in Minnesota and Wisconsin were gouged out by glaciers and later
filled with glacial meltwaters. The old Teays River drainage system
was radically altered and largely reshaped into the Ohio River
drainage ystem.
Other rivers were dammed and diverted to new channels, such as the
Niagara, which formed a dramatic waterfall and gorge, when the
waterflow encountered a limestone escarpment.
In between ice ages, there are multi-million year periods of more
temperate, almost tropical, climate, but also within the ice ages
(or at least within the last one), temperate and severe periods
occur. The colder periods are known as glacial periods, the warmer
periods as interglacials. The Earth is in an interglacial period
now, the last retreat ending about 10,000 years ago.
"As a huge Stone is sometimes seen to lie
Couched on the bald top of an eminence;
Wonder to all who do the same espy,
By what means it could thither come, and whence;
So that it seems a thing endued with sense:
Like a Sea-beast crawled forth, that on a shelf
Of rock or sand reposeth, there to sun itself."
W Wordsworth 1807 The Leech Gatherer
To log this cache, you must e-mail me some information regarding
the site that you learned while there. This could be done by
answering one or more of the following questions:
1) What is the rock's height, diameter, length, radius,
circumference, etc. (Choose one or more)
2) You could also try and calculate the approximate mass of the
rock. The density of granite is approximately 2600 kg per cubic
metre. Using your size measurements (length x width x height) you
can calculate the mass if you know the density. (I don't think this
rock is actually made from granite I just chose granite because I
don't know what the rock is made of so you can use granite or a
different type of rock as long as you tell me what kind of rock you
are using for your density calculations).
3) If you do know what type of rock this is, you could also use
that as your answer.
To confirm that you visited the site you must also show a photo of
you and or your GPSr with the rock. Any logs that do not meet the
requirements will be deleted because Earthcaches are now meant to
be educational.
Thank you for visiting my Earthcache.
Additional Hints
(Decrypt)
Ovt Ebpx