Bisbee daily review., 1918-01-20


 of how it came to be made up in this way. As the earth is merely one of a myriad of other bodies floating around in space. the study of geology has to include a part at least of the study of astronomy.
 Here in BiSbee we have all seen the beds of SandstOneS and shades, mak- ing up the hills tO the north of Low eli. To produce these beds the wear ing action of rains on the land and the action of the sea waves on a rocky coast explain how they were formed. Therefore. geology has to include the study of the form of the earth the ae- tion of air currents to produce rain. the temperature. magnetism. present life. etc, or the study of physiogra- phy.
 | In our study of geology we find a very large part of the crust to be made up of old lavas from extinct vol canos. To study these lavas and their effects on the other rocks with which they come in contact. it is necessary to study two more things-chemistry and mineralogy. Chemistry tells us ex- actly what is in everything and min eralogy tells us what form certain chemical combinations take. SO that we can tell them at a glance.
 We all know that large part Of the crust Of the earth is made up of limestOnes, which were formed from the remains of sea shells, fish. bones, etc. Coal seams also make up con siderable part of the crust. and these. as we know. were originally swamps aad forests, whicI have been buried and compressed. So geology has to take in to a large ext -nt the study oI animal and plant life or biology.
 To go over what l have already said. ' geology has to include astronomy. biology, physiography. chemistry and minerslogy and mechanics. So you can see that have a pretty big job on hand to tell you all about geology in two-hour lectures. In these lee. lures am going to state a lot of facts which have been proved to be true. and which you will have to swallow whole. To any one wishing to find the proof to any of my statements, ] will be glad to refer him to books which can be obtained in the library here n Bishee.
 l The rocks forming the earth'S crCst can be divided into three families , Sedimentary, Volcanic and Metanor- phic. Sedimentary rocks are those which have been laid down mostly under water either at the bottom of , the sea or at the bottom of lakes. The material making up these rocks Origi- nally came from the land and was . put there by rivers flowing into the sea and lakes. They were also form | ed by the skeletons of animals. shells. decayed wood. etc. Sedimentary rocks always take the form of layers or beds. Here in Bisbee We are an familiar with beds of limestone. sandstone and shale. covering almost the whole surface south of Tombstone Canyon and Mule Gulch.
 Volcanic rocks are those which came up from the bowels of the earth through cracks in a melted state. Sometimes they came 10 the surface through volcanoes. and at other times they never reached the surface. They are easily recognized by the irregular shape which they take with respect to the rest Of the formation. and by , their being made up Of crystals tn- stead of rounded grains, Ii a volcanic rock comes tO the surface through a volcano. we also get another kind ot volcanic rock thrown out or rolling out over the surface. These are called tufts and lavas. They will 6e bedted just like a Sedimentary rock. but usually show their origin by the cryS- talS or by their resemblance Co slags from shelter. Here in Bishee we don't run across any of these kinds ot rock.
 MetamOrphic rocks are rocks that used 10 be either sedimentary or vol canic rocks. but which have been crUmped up and changed by great pressure. This pressure may be caused by one or both of two things; (l) the crumpling of the crust of .he earth due Co the slow cooling and shrinking of the interior; or, (s) the weight Of sediments on top. Here m Bisbee We have an example Of this family of rocks in the Pinal SchiSt. on which a large part Of the town ot BiSbee Is built.
 In the study of geology the impOr- tant thing Co always bear in mind is that in the history of the earth mil lion years Is mere second Of time. Our earth is millions and millions of years old. To bring this out here in Risbee. l will illustrate it by Fig. l. This is vertical section taken through the Lowell shaft and Saera- mento Hill looking west. The black line represents the present surface, and an attempt is here made to build up the probable surfaces at different geological ages. The wavy green line represents the probable surface at the earliest known geological time. This surface was an old land surface of schist. worn down by the action of the clements to a nearly level plain, just about at sea level A slow sink ing of this land surface then took place below the sea and 44O feet of the first sedimentary formation. con sisting of conglomerates and sands