Making mountains

2010 ◽  
Author(s):  
Jan Zalasiewicz
Keyword(s):  
North America ◽  
Coastal Plain ◽  
Mountain Building ◽  
Sea Floor ◽  
The North ◽  
Iapetus Ocean ◽  
Rivers And Lakes ◽  
Northern Continent ◽  
Minor Distortion ◽  
Surface Changes

It has been a quiet 20 million years for the pebble: an interlude, at somewhere around 3–4 kilometres under the sea floor. The rock has still been crystallizing, but only very slowly. The water has by now mostly been squeezed out, so little fluid has flowed through that rock. At this depth it is hot, well above 1008°C. The pebble-form is sterile, lifeless. The time is now a little under 400 million years ago. We are in the Devonian Period. Above, at the Earth’s surface, changes have been taking place, but as far as they affected the pebble they could be on another planet. In the sea, the graptolites have been going through an evolutionary rollercoaster, with explosions of diversity separated by bad times, when they only just survive. Soon, one of those bad times will be terminal, and they will disappear from the open seas, never to return. By contrast, the fish are beginning to thrive both in the sea and in rivers and lakes. The land is greening, almost explosively, as plants evolve furiously. None of this affects the future pebble. But something soon will. The sea above has been gradually shallowing, filled in with sediment from the encroaching land. Eventually, it changed, some few million years ago, into a vast coastal plain, traversed by rivers. We are about at the time, now, when that lowland is about to rear up to form a range of mountains that—although much reduced from their early glory—can still be climbed today. What took them so long? For the Iapetus Ocean to the north, which, 50 million years ago, was more than 1000 kilometres across, had effectively disappeared 20 million years ago, the ocean plate sliding beneath the northern continent of Scotland and north America. But on Avalonia, the effect was as if these continents had just slid neatly into place, with only minor distortion of the Avalonian crust (and, in truth, these landmasses did approach each other partly from the side, rather than headon). Did the mountain-building force still come from the north, perhaps as some mysteriously delayed intensification of the vice-like grip that held these landmasses together?

Illuminating the lack of consensus among descriptions of earth history data in the North American deserts: A resource for biologists

2010 ◽  
Vol 34 (4) ◽  
pp. 419-441 ◽  
Author(s):  
Joseph S. Wilson ◽  
James P. Pitts
Keyword(s):  
North America ◽  
North American ◽  
Western North America ◽  
Mountain Building ◽  
History Data ◽  
Earth History ◽  
The North ◽  
Robust Model ◽  
History Of ◽  
Geomorphological Evolution

Understanding the timing of mountain building and desert formation events in western North America is crucial to understanding the evolutionary history of the diverse arid-adapted biota that is found there. While many different, often conflicting descriptions exist regarding geobiotic change in western North America, little work has been done to synthesize these various viewpoints. In this paper we present several case studies that illustrate the differences in the various explanations, based on geological and paleobiological data, detailing mountain uplift and desertification in western North America. The majority of the descriptions detailing mountain building in this area fall into two major periods of uplift, the Laramide uplift (∼70—50 Ma) and the Neogene uplift (∼15—2 Ma), yet it remains unclear which of these events was responsible for the formation of the modern mountains. Like the descriptions of mountain building, various accounts exist detailing the timing of desert formation. Some authors suggest that the deserts existed as far back as 15 Ma while others propose that desert formation occurred as recently as 10,000 years ago. Based on this review of the literature, we suggest that the data on Cenozoic geomorphological evolution of the North American desert landscape is still too coarse and filled with gaps to allow for the development of a robust model of landscape evolution. Instead, this work demonstrates the need for biologists studying the North American biota to realize just how problematic some of the earth history data and models are so that they can build this uncertainty into biogeographic reconstructions.

Lyell on the Geological Similarity of North America and Europe

1982 ◽  
Vol 1 (1) ◽  
pp. 45-47
Author(s):  
Leonard Wilson
Keyword(s):  
North America ◽  
Coastal Plain ◽  
North American ◽  
The United States ◽  
Atlantic Coastal Plain ◽  
Fossil Plants ◽  
Land Area ◽  
The North ◽  
The Difference ◽  
Atlantic Coastal

During his travels in America in 1841-1842 and 1845-1846, Charles Lyell was impressed by the difference of the living flora and fauna of North America from those of Europe. The fossil shells of the Cretaceous strata of New Jersey and of the Tertiary formations of the Atlantic Coastal Plain of the United States showed that North America had also constituted a separate biological region during the Cretaceous and throughout the Tertiary. By contrast, the fossil plants of North American coal formations were so closely similar to those of Europe that Lyell concluded that during the Carboniferous, Europe and North America must have formed a continuous land area. As evidence of a former land connection between North America and Europe, Lyell observed that the distribution of sediments among the strata of the Appalachians indicated that the Carboniferous strata of North America had been derived from land lying to the East — where the Atlantic Ocean now is. Similarly, the North American Silurian and other Paleozoic systems contained fossils similar to those of Europe, and their sediments were so distributed as to suggest that they had been derived from land lying to the East. Lyell pointed out the ancient uniformity of European and American fossil life, without being able to explain it.

The oil window

2010 ◽  
Author(s):  
Jan Zalasiewicz
Keyword(s):  
Plate Tectonics ◽  
Mountain Building ◽  
Sea Floor ◽  
Mountain Ranges ◽  
South Wales ◽  
Iapetus Ocean ◽  
The Creation ◽  
Splendid Isolation

It is a few million years later—perhaps three, perhaps five. Sediment has been pouring onto a Silurian sea floor that will, much later, be sliced into by a different sea and become the rugged cliff-fringed coastline of central Wales. It has been pouring in so thick and fast that our pebble stuff is now some two kilometres or more down below that sea floor. This is quite rapid burial, even by geological standards, and one can blame changing geography for that. To produce a lot of sediment, there is need for a lot of erosion, and also for the production of something that can be eroded—that is, uplands and mountains on land. On Earth, such production of topography is supplied by the marvellous machine of plate tectonics. And at that time, the ocean between Avalonia and Scotland, that we call the Iapetus Ocean, had just about closed, and those two landmasses were just beginning to nudge into each other. Soft collision, it’s called, when the pressure from the adjoining continents is just enough for sections of crust to begin to be pushed up and (to compensate) pushed down in different places—but not enough for the wholesale crumpling that goes with the creation of great mountain ranges. Thus, the landmass that was then in, and just south of, what is today South Wales was driven upwards, while the floor of the sea that then covered Wales was forced downwards. The resultant flood of sediment was Nature’s means of trying to restore equilibrium. Here, the particular pattern of squashing of the pebble stuff is linked with those enormous, mysterious movements of continents hundreds and thousands of kilometres away. And mysterious they certainly were, for on the heels of the soft collision should have followed the hard collision and mountain-building. But it didn’t. The mountain-building did take place—but only eventually, and not until many millions of years later. The Welsh mountains are quite a bit younger than they should be—and so that story will have to wait. Another story developed in splendid isolation from such tectonic violence. We can showcase it now.

Political orientation and moral foundations

2019 ◽  
Vol 118 (11) ◽  
pp. 365-371
Author(s):  
J Dorasamy ◽  
Mr Jirushlan Dorasamy
Keyword(s):  
South Africa ◽  
North America ◽  
American Studies ◽  
Political Orientation ◽  
The Political ◽  
Moral Foundations ◽  
Open Approach ◽  
Online Questionnaire ◽  
Moral Foundation ◽  
The North

Studies, especially in the North America, have shown a relationship between political orientation and moralfoundation. This study investigated whether moral judgements differ from the political orientation of participantsin South Africa moral judgment and the extent to which moral foundations are influenced by politicalorientation.Further, the study investigated the possibility of similar patterns with the North AmericanConservative-Liberal spectrum and the moral foundation. There were 300participants, 78 males and 222 females,who completed an online questionnaire relating to moral foundation and political orientation. The results partiallysupported the hypothesis relating to Liberal and Conservative orientation in South Africa. Further, this studypartially predicted the Liberal-Conservative orientation with patterns in the moral foundation, whilst showingsimilar findings to the North American studies. A growing rate of a neutral/moderate society is evidenced in SouthAfrica and abroad, thereby showing the emergence of a more open approach to both a political and generalstance.”””

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