Quantitative skills: do geologists need them? Presenter: Dr. Yuri Gorokhovich, Lehman College Things to consider: Geology is not just oil and gas. It is a system of knowledge about relationships between (mostly inorganic) natural systems on the Earth. It is all driven by plate tectonics and rock cycle! Relationships in nature (e.g. hill slope and river; mountains and weather; coast and delta; etc.) are complex and non-linear. Therefore they have to be formalized. Examples of such formalization: hill slope – contour lines; coast – line; delta – area; mountain peak – point, sand – size, mud – physical variable (strength, viscosity, size), rock – texture, mineral - hardness, etc. Formalization uses numbers and spatial patterns. Because relationships in nature and formalization connect physical and chemical processes at different scales numbers and patterns play important role. Numbers – math; patterns – geometry.

Main Geologic Theories Plate Tectonics Rock Cycle

Global Schematic View of Plate Tectonics

Cartographic Scale – key to measurements on Earth Verbal or descriptive map scale: one unit on the map = so many units on terrain. For example, on the figure below, scale 1 / 94,000,000 means: 1 cm on the map = 94,000,000 cm on the terrain. Note that units in left and right sides are the same, i.e. cm. They can be in inches also. Bar scale is a bar with subdivisions and explanation of units. It is convenient for measurements of the distances on the map.

Use of Plate Tectonics and Cartographic Scale The evolution of the San Andreas fault system over the last 30 million years is shown on the graph above. The Pacific plate currently is moving past the North American plate at a rate of about 3.5 cm/year. Using the scale on the map and the rate of plate motion, determine how long (in million years) it will take Los Angeles to reach San Francisco.

Use of Plate Tectonics and Patterns ATLANTIC OCEAN Isochrones: lines connecting points of the same age. For Atlantic Ocean isochrones were calculated from basalt samples taken from the ocean bottom. 400 800 1200 1600 2000 2400 2800 km On average, the Atlantic Ocean is growing at a rate of about 2.5 cm/year. Based on that, calculate the following: How much the Atlantic Ocean has grown since Columbus sailed in 1492? How much the Atlantic Ocean will grow in the next 200 years? Looking at the patterns of isochrones between Africa and North America answer the following: How old is Atlantic Ocean (approx.)? Is spreading rate of 2.5 cm/year a constant over the life of Atlantic Ocean? When (range of millions of years) the spreading was the fastest? When (range of millions of years) the spreading was the slowest?