OliD liAI^E RGASSIZ. 



Surface Geology of the Red and Assiniboine Valleys. 



Dr. Bryce Explains the Formation Existing- in Manitoba by the 



Theory of Glacial Action.— Interesting- Accounts of the 



Orig^in of Stony Mountain and Bird's Hill. 



The lecture by Rev. Dr. Bryce before the 

 Historical and Scientific Society Thursday 

 attracted a larpfe audience to the ".ity hall. 

 The chair was taken by Rev. A. B. Baird, 

 and when the meeting was called to order, 

 Rev. Dr. Bryce began his lecture, on "Old 

 Lake Agassi z," and the surface geology of the 

 Red River and Assiniboine 'alleys, speaking 

 as follows : 



In the summer of 1887 there called upon 

 the writer, in Winnipeg, a studious looking 

 young man, whose address was given as Mr. 

 Warren Upham, Somerville, Massachusetts. 

 Mr. Upham said that with a companion he 

 was engaged in examininer and measuring the 

 various ridges that on the slopes of Pembina 

 Mountains, Tiger Hills and Ridin? Mountain 

 are found so abundantly, rising one above 

 the other. Mr. Upham explained the object 

 of his visit, and said that the Minnesota 

 geologists had been examining these ridges 

 as far back as 1879, and that indeed Major 

 Keating as long ago as 1823 had called atten 

 tion to these marked surface features. The 

 study of Mr. Upham and others including 

 our own Canadian geologists has led to the 

 unravelling of the mystery of our prairies 

 and to-day we have reached geologic 

 certainty on almost all essential 

 points as to their formation. 



THE ROCK HISTORY. 



As well known even to the tyro, the rocks 

 underlying the soil or drift deposit of Mani 

 toba and the Territories are largely limestone 

 and sandstones deposited ages ago. These 

 were formed by the action of climate and 

 water agencies, wearing down the rocks of the 

 great Laurentian belt lying to the east of us 

 in Keewatin and Northwest Ontario. Raised 

 above the water, these rocks, chiefly limestone 

 as found at Selkirk, Stonewall, and generally 

 under our prairies, remained exposed to the 

 action of the weather, and no doubt became 

 honeycombed and loose, and easily removed 

 for a considerable depth. We estimate that 

 one hundred feet or more of this fragile rock 

 thus removed lay over the site of Winnipeg. 

 At length changes in the earth's climate took 

 place, so that while at the time of the forma- 

 tion of these Silurian rocks there had been a 

 hie:h temperature and warm seas in which 

 grew vast colonies of coral, in this later time 



following the upheaval of the Rocky moun- 

 tains, there came a period of great cold. It 

 ib not our work this evening to speak of the 

 causes of this change, which took place in 

 what is generally known as the glacier period, 

 but simply to note the undoubted fact. 



THE AGE OF ICE. 



The beginning of this period of cold was 

 probably not less than from 150,000 to 200,- 

 000 years ago- Gradually the land sloping then 

 as now, to Hudson Bay, became covered with 

 snow, and this became too heavy for the sun 

 to melt, and thus rose great beds of ice such 

 as we see in the bosom of the Rocky mountain 

 valleys to day. Century after century the 

 ice built higher, and extended further south. 

 It is believed that at some points there was a 

 depth of from 6,000 to 10,000 feet of ice, and 

 W3 know that the icy sway was continued as 

 far south as the latitude .39 ° n , or nearly to 

 St. Louis, at the mouth of the Mit^souri 

 river. At length came a time when internal 

 changes of the earth's crust banished the 

 reign of winter for a while from much of this 

 region, but again a second glacial period visit- 

 ?d the earth, and the ice in great fields was a 

 second time piled up. The departure of this 

 second vast ice field is what left the surface of 

 our prairies in their present condition ; and 

 the beginning of this latter period has been 

 estimated at from 5,000 to 7,000 years ago. 

 Mr. Upham's surmise is that the removal of 

 the ice from the south of the Red river valley 

 down to Hud«on Bay may have been done in 

 perhaps one thousand years. Others speak of 



longer time. 



OLD LAKE AGASSIZ. 



Some 2.50 miles south of Winnipeg, on the 

 western boundary of Minnesota, a valley is 

 seen 125 to 150 feet deep, with a width of 

 about a mile and a half. This connects the 

 valley of the Red river with that of the 

 Mississippi, and here the drift of the water 

 ^•hed was cut throtigh by a great river. The 

 valley has been partly filled up again by 

 tributary streams, but in the south end of it 

 is Big Stone lake emptying into the Minne- 

 sota river, a tributary of the Mississippi, and 

 in the north of it Lake Traverse running into 

 the upper branch of the Red river. When 

 the ice of the glacial period reached this 

 point in its withdrawal there was no valley, 

 but a lake began to form north of the height 

 of land and bounded by the lobe of the 



