Lab One Observing and Measuring

Earth Materials and Processes

 

 

·       Objectives:

1)      Identify and describe earth materials and processes

2)      Measure and calculate length, area, volume, mass and density

3)      Develop and test physical and quantitative models of isostasy based on floating wood blocks and icebergs…apply to the earth

4)      Analyze earth’s global topography and the hypsographic curve-  related to isostacy??

 

 

·       Two kinds of Data…

       

Qualitative-  Observations and Descriptions

 

Quantitative-  Data obtained by measuring  changes in time and space.

 

·       Measurements and Conversions…

 

Linear Measurements:  One dimensional measures of lengths and distances.

 

ex-  The distance from Pullman to Moscow is 8 miles

 

 

Area Measurements:  Two dimensional measures of space. 

 

ex-  A field is 10ft wide and 5ft long (linear measures) so the field occupies an area of  10ft x 5ft = 50ft2

 

Volume Measurements:  Three dimensional measure of the space an object occupies.

 

ex-  A cube has a length of 5cm, a height of 10cm and a width of 2cm…so the volume the cube occupies in space is L x W x H

 

or 5cm x 10cm x 2cm = 100cm3

 

OR

 

To find the volume of an irregularly shaped solid, use a graduated cylinder and determine how much water the object displaces, that is its volume.  convert ml to cm3

 

1ml = 1g = 1cm3

 

 

 

 

 

 

 

Conversions… converting one unit to another ie. cm to m

cross canceling units-

 

convert 4300ft to miles then km…

 

4300ft x  1mile  x     1km      =  1.31km

1         5280ft    .6214mile

 

Mass:  Measure of how much an object weighs in earth’s gravity.

 

ex-  4ml of water weighs 4g (from conversion above)

 

Density:  Measure of an objects mass per unit of volume…reported in g/cm3 

 

ex-  A rock has a mass of 45g and occupies a volume of 30ml…

So- first convert 30ml to cm3  30ml x 1cm3  = 30cm3

                                                    1        1ml

 

Then- put mass over volume and divide… 

 

45g / 30cm3 = 1.5 g/cm3

 

 

Questions so far…………….

 

 

 

 

 

Buoyancy and Isostasy….

 

Buoyancy:  Why does a block of wood float in water??

 

A fluid, like water, pushes in all directions…

 

When an object, like a wood block is placed in water- the water pushes on its sides in all directions…

 

The opposing forces on each side of the block cancel each other and the only force that is left is a force pushing upward on the bottom- the buoyant force

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Isostasy:

 

The reason an object floats is that it displaces an amount of water equal to the weight of the object- allowing the buoyant force to support the object.

 

 

Definition:  Isostasy is the balancing condition between the object and the displaced water. 

 

·      How high out of the water an object floats is determined by its isostasy.

·         A lighter material will float higher because it doesn’t need to displace as much water to float, allowing it to rise above a denser material that must displace a greater amount of water, causing it to sink lower.

 

 

 

To Determine Isostasy you will need….

 

HTotal      The total height of the block

H­­Below­­     The height of block below waterline

HAbove     The height of block above waterline

rwater       The density of water

rblock       The density of wooden block

 

look at fig 1.16

 

Now,

 

Think about these principles applied to the earth, remembering that the continental crust is composed of less dense materials and the oceanic crust is composed of more dense materials.

 

Some Terms-

 

Bimodal??  Means two peaks on a graph  see fig 1.17 on pg. 26

 

Hypsographic??  A graph on page 26 that shows height in km on the y axis and the percent of the earth at that height on the x axis

 

 

 

 

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