salam to all. guys my friends have requested me to make notes of physical geo.bcoz they are having difficulty in making notes. so i am starting notes of physical geography,you can also contribute as much you can and if any one find any mistake plz inform me. me ALLAH pak se dua kerti hun k wo mujhi itne hemat de k ma ye notes time pe complete ker sakun.ameen



physical geography notes

first topic THE UNIVERSE

The Beginning1,2

The Solar system started with the collapse of a cloud of interstellar gas and dust. Gravity caused the cloud to fragment and condense into ball of heated gas that eventually became the Sun. Meanwhile, whirling disks around the nascent star gave birth to the planets. About 4.5672 billion years ago bits of dust around the growing Sun started sticking together to form small, inch-long clumps (reproducible in the laboratories). The next step was amalgamation of the small bits into mile-wide objects call planetesimals.








Figure illustrates the successive stages in the earlier growth of planet Earth


The three illustrations below provides a reasonable conjecture on further development of the Earth 4.5 billion years ago. Figure 09-01 shows a larger planetesimal attracting the smaller ones from the surrounding dust clouds. This nondescript rock will have a more spherical shape when it reaches a diameter of 500 km. Figure 09-02 shows a half-sized Earth. It was a heavily





Earth embryo 4560 my ago





Earth,half sized,4550 my ago




Earth,primitive,4540 my ago

cratered world covered with magma produced by planetesimal impacts. The new world was beginning to acquire a thin atmosphere. The cloud patterns are more belt-like because of the faster rotation. Figure 09-03 shows a primitive



2 :-Geological and Biological Records

A more reliable history for a small part of the Earth can be found in Strathcona Park, Vancouver Island, Canada; or any places where sedimentary rocks, such as clays, shales, and limestones, are exposed. Figure 09-04a depicts the sequence of rocks






stratigraphy) that occurs within the park and immediately adjacent to it, including the names and ages of the natural rock layers or strata. The bottom layer (earliest) corresponds to the Devonian Period when earliest amphibians and first forests appeared about 400 million years ago. The Strathcona Park website carries all the information about the geology of the Park and more. While the events and objects listed in Figure 09-04a are related locally within the Park, the history of the Geological Periods in Figure 09-04b is supposed to be global with events re-constructed by geologists and paleontologists. Table 09-01 depicts the geological and biological events in each of the period.








to be continued.................