Download Whadda Ya Know `Bout Geology

Whadda Ya Know ‘Bout Geology?
1
What is geology?
The study of the Earth: its physical characteristics and its processes.
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Why is it important to have at least a basic understanding of geology in life? Because the basics
for human (and every living thing on the planet) habitat - food, shelter and water - comes from the Earth’s
crust. Raw materials and/or minerals in the ground to build the infrastructure and economies of societies
come from the ground. Oil, coal, natural gas, wood and nuclear materials, the main ingredients for the
world’s energy system, all come from the ground.
water and septic/sewer systems for individual homes, cities, states and nations;
arable (farmable) areas that are available currently and in the future with global climate change;
materials for all shelters come from the crust;
everything - indoors and out - we see around us came from the crust of the Earth;
energy sources come from the ground
human history is full of war and conflict over these items (Look at what’s happening today in the Middle
East!)
3
How were the Earth and Moon formed, and about how long ago? Smaller bits of gas and dust
collected through the force of gravity and built into larger clumps of material. Clumps continued to grow,
and as they did, the gravitational force grew as well. This allowed for more planet building material to be
collected from a larger area. Eventually, all of the nearby planet building material was gathered into what
is now the Earth and Moon.
The Moon was created towards the end of the major planet building episode, about 4.6 billion years ago, by
a Mars-sized planet colliding with the Earth. The off-center collision splashed molten material into space
which clumped together under the force of gravity to become the Moon. Evidence for this theory include the
Moon’s orbit is moving farther away each year as a result of the momentum of the impact. The distance
increases at about an inch a year. The Moon is a little over a yard (or meter) further away from us than the
last time people were on the Moon in 1972! In addition, the Moon’s orbit of the Earth is not equatorial, but
angled at about 5 degrees from our Equator, also as a result of the off-center impact. If the Earth and Moon
formed peacefully side by side, logic dictates that the Moon would orbit our equator.
[ This is why we do not have Lunar and Solar eclipses each month. (Wouldn’t that be cool?) Most of the
time, the Moon passes above or below the line of sight of the Sun during the New Moon phase (instead of
causing a Solar Eclipse) or above and below the Earth’s shadow in space (instead of causing a Lunar
Eclipse). Evidence for the smaller bits gathering into bigger bits for planet formation: every solid body in
the solar system exhibits evidence of these collisions of smaller bodies into larger ones. They’re known as
craters. Most of the craters on Earth have been covered by the ocean or erased by eons of weathering and
erosion, biological activity and/or the movement of tectonic plates. But there still are craters evident all
over the planet. Every time you see a shooting star, or meteor, you are witnessing the burning up in our
atmosphere of a small particle of space dust, rock or ice that has collided at high speed (often measured in
thousands of miles per hour). The building blocks of planets are still being collected at the rate of about ten
tons per day here on Earth!) This occurs only 60 to 80 miles up in our atmosphere. So you see, shooting
stars (or falling stars) are not stars at all!]
4
What happened to the Old Man of the Mountain? The Old Man was both created and destroyed
by the processes of weathering and erosion. Granite is composed of three minerals: quartz, mica and
feldspar. The feldspar in the pinkish/salmony Conway Granite, which is what Cannon Mountain is made of
(the Old Man was located on one of the slopes of Cannon Mountain), is easily dissolved by water. When
water penetrates the rock and freezes repeatedly, it expands and contracts, applying pressure on the rock.
This can cause it to crack and split (a process known as calving). This breaking up of larger earth materials
(rock) into smaller pieces is known as weathering. Since the sections of rock that made up the profile of the
Old Man were situated high on a steep mountainside, gravity is what caused the weathered sections of stone
to move from the top of the mountain to the bottom. The movement of earth materials from one place to
another is known as erosion.
5
Where did the oldest rocks in NH form? Best estimates for the origins of the oldest rocks in the
state (the Massabesic Gneiss (pronounced ‘nice’) found near Manchester [see rock cuts in the area of exits 8
and 9 on I-93]) are that they were formed near the current position of Antarctica nearly a billion years ago.
Through the movements of the tectonic plates that make up the earth’s crust, they ended up here in modern
day New Hampshire.
6
What is below your feet? socks, shoes, [carpet/wood/linoleum or other flooring covering material
then wood or concrete if indoors] dirt (and other earth materials such as sand, gravel, clay silt, etc.),
bedrock (which is the crust of the Earth), the molten rock of the mantle, the liquid outer core of iron and
nickel (principally), the solid inner core of iron and nickel (principally).
7
Look around the room and identify an object. Where did the materials come from to make it?
From the crust: metals from ores, wood from trees that get their nutrients and water from the ground
and plastics from oil. Sheetrock is made from gypsum (and paper - a wood product) that is mined
from the crust. Concrete is principally made of sand and gravel (earth materials) cemented together.
Whatever you do, don’t ever call concrete ‘cement’ in front of a civil engineer. They will be quick to
point out that cement is only one ingredient in concrete. They will argue you might as well call
concrete ‘sand’ as well! For more, see response to question #2 above.
8
What caused the White Mountains of NH to form? The collision of the North American tectonic
plate with the African and European plates that started about 300 million years ago pushed up the
Appalachian mountain chain until they were as tall as the Himalayas are today (if not taller!). Since the
continents started drifting apart about 180 million years ago, the mountains stopped being pushed up and
have been subject to the wearing down and removal processes of weathering and erosion. Where did all this
material go? It was carried out to see by rivers draining the land or pushed up in a plow-like fashion by the
advancement of large continental ice sheets and created Cape Cod, Long Island (NY), Block Island,
Martha’s Vineyard and Nantucket.
Some mountains in the Whites are volcanic in nature (see the orangish and yellowish colors that align nearly
North-South in the Bedrock Geologic Map of NH). These mountains include among them Cannon Mountain,
the Ossipee Mountains and Pawtuckaway Mountains. The Ossipees are the only true volcano that existed in
the state. There the lava ( molten rock that has reached the surface) erupted onto the landscape. The other
volcanic (igneous) mountains were formed from magma which is molten rock that got near the surface
(within a couple of miles), but didn’t quite break through. This North-South pattern of volcanically created
mountains were created possibly along a failed rift when the North American continent separated from the
African and European plates about 180 million years ago.
9
How old are the White Mountains? If they’re metamorphic in nature, they’re probably about 300
milion years old. If they’re igneous in nature, they’re probably about 180 million years old. For more, see
the response to question #8.
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How are Mt. Washington and Mt. Monadnock alike? They are both made of highly erosion
resistant rock surrounded by relatively easier to erode rock. This makes them stand out much higher than
the surrounding terrain they are located in. Both mountains, along with others in the state, Mt. Moosilauke
for instance, were formed from sea floor sediments that were caught up in the giant squeeze of the
continental collisions that started about 300 million years ago. This squeeze generated tremendous amounts
of frictional heat and pressure for prolonged periods of time. This heat and pressure baked the sediments
into the very hard rocks they are today.
Things to know:
mineral
inorganic (non-living) substances that have their own characteristic appearance (can be
crystalline) and chemical composition.
rock
a combination of minerals
granite
rock composed primarily of the minerals quartz, mica and feldspar, forms 3 to 5 miles below
the surface allowing the molten rock to cool slowly and grow crystals of the 3 minerals. The
larger the crystals, the longer the cooling period.
3 types of rock:
igneous - volcanic in nature; derived from molten rock solidifying
sedimentary - derived from the settling of sediments of earth materials and organic
matter into layers with the lower layers being compacted and cemented into rock by
the weight of the overlying layers.
metamorphic - [meta=all or whole; morphic=changing] the changing of an existing
igneous, sedimentary or other metamorphic rock into a rock with new chemical and
physical characteristics derived from great heat and/or pressure being applied.
rock cycle - the ability for any one of the three types of rock to turn into a different kind of one of three
kinds
of rock given weathering, erosion, movement of tectonic plates and time.
earth material - inorganic matter that makes up the crust and soils on the surface of the Earth. (sand, gravel,
clay, silt, etc.)
weathering - the wearing down of earth materials from larger pieces into smaller ones.
erosion - the transportation of earth materials from one place to another by wind, water, glaciers or gravity.
A Short Geologic History of NH
New Hampshire’s landscape has been created by at least 4 collisions and separations of tectonic plates
during the course of the planet’s history. during each collision and separation, new pieces of continental
crust were added to this piece of North America. There are rocks that used to be sea floor sediments ( check
out the rocks along the Mount Washington Auto Road for example), trapped tropical, volcanic island chains
(the Bronson Hills on the NH Eastern shore of the Connecticut River from the Mass border to about
Hanover) and volcanoes (the Ossipee Mountains). On the Bedrock Geologic Map Of NH, there are 4 color
trends - corresponding roughly to the collision/separation events - starting in the Southwest corner of the
state and arcing to the Northeast.
The White Mountains were created starting about 300 million years ago when the North American tectonic
plate collided with the African and European plates, pushing up the Appalachian Mountains until they
rivaled today’s Himalayas or Andes mountains.
About 180 million years ago, the continents started to drift apart, causing ruptures, or rifts, in the Earth’s
crust. The main rift that took effect is located in the middle of the Atlantic Ocean today and the continents
continue to spread apart at about the same speed your hair or finger nails grow. (about 1 to 3 inches on
average) A failed rift is thought to have formed slightly to the west of the existing one allowing molten rock
to intrude into existing rock. On the Bedrock Geologic Map Of NH, these rocks tend to be yellowish or
orangish in color and tend to align nearly North South in the state. Only the Ossipee Mountains actually
broke through the surface of the crust to become a volcano. The rest of the igneous rock made it close to the
surface(3 to 5 miles), and cooled there. Over the past 180 million years, weathering and erosion have worn
all mountains across the state down to their roots. The remains of the once mighty mountains have been
washed out to sea via rivers and glaciers or bull dozed in front of advancing ice sheets to create Cape Cp,
NY’s Long Island, Block Island, Martha’s Vineyard and Nantucket Island.
NH’s landscape has been shaped most recently by the advancement and retreat of the glaciers during the Ice
Age that ended here around 10,000 years ago. Many glacial features are visible today: lakes, kettle hole
ponds, notches, sheep back, or roche moutinee, shapes to mountains (gently sloping north and west facing
sides of mountains indicating which direction the glaciers moved in from, and steeper south and east facing
slopes where the advancing glaciers plucked off pieces of the mountains); glacial boulders, and u-shaped
glacially carved valleys.
Know this stuff and you will have earned the “Walking, Talking Geo Geek Status” you all deserve. Enjoy!
Dan Reidy
Moultonborough Central School
Moultonborough, NH
Christa McAuliffe Sabbatical Fellow 2003/2004
Author of http://www.nhgeology.org - the Geology of New Hampshire web site