Plate Tectonics

What evidence supports the idea of plate tectonics? (5 reasons) 1.The Earth’s modern day continents seem to ‘fit’ together 2.Fossils of similar species were found on continents that are now separated by a great distance 3.Evidence of glaciers exists in parts of the world that do not currently experience freezing temperatures (this implies that landmasses move throughout time)

What evidence supports the idea of plate tectonics? (5 reasons) 4.Paleomagnetic studies of Earth’s past magnetic fields suggest the magnetic north pole has changed. A parsimonious (simple) explanation is that landmasses have moved, NOT the north pole. Stripes within magnetite (magnetic magma mineral) imply movement of materials in the lithosphere 5.Seismometers used for weapons testing after WWII showed a pattern of earthquake and geologic activity. This suggests boundary lines

What is a mobilist? What is an anti- mobilist? People (geologists) that believe the features of the Earth is a result of massive global contraction and expansion are called ANTI- MOBILISTS People (geologists) that believe the Earth is made of moving pieces are MOBILISTS

What was Pangaea? Approximately how long ago did it exist? The ‘SUPERCONTINENT’ existed about 225 million years ago

What are the names of the two ‘pieces’ of Pangaea during the Triassic period? Laurasia and Gondwanaland

Supercontinent Cycle Supercontinent cycle: The aggregation and dispersal of Earth’s continental crust in million year cycle Wilson cycle: Describes the periodic opening and closing of ocean basins Although complementary, the Supercontinent cycle is more compelling since the oldest seafloor is dated 170 million years ago and the oldest continental crust is dated 4 billion years.

What drives the movement of plates? The movement of plates is driven by convection currents within the Earth

Push

How are the two major ocean masses, the Atlantic and Pacific, changing? The Atlantic ocean is getting wider and the Pacific ocean is becoming narrower *** The Pacific ocean may close in the future and form the Mega Pacific Ocean through tectonic interactions. This Mega ocean will surround the new supercontinent. (~ years)

When was the theory of plate tectonics formulated? 1960’s and 1970’s

How many tectonic plates exist? What are their names? 14 major plates + 38 minor plates = 52 plates

How fast do plates move? 2 – 10 cm per year

3 Types of plate boundaries. Convergent boundaries describe compression Divergent boundaries describe extension Transform boundaries describe sliding or irregular interaction

Boundary between Eurasian and North American continental tectonic plates

San Andreas Fault – Transform Boundary

Types of crust Oceanic crust surfaces underneath ocean basins. ▫Thin ▫Dense ▫Continually made at mid-ocean ridges Continental crust exists above water and at shallow sea beds ▫Thick ▫Low density

Subduction Subduction refers to the movement of one plate under another plate at a convergent boundary

3 types of convergent boundaries Type of convergent boundary Result Oceanic crust – Oceanic crust One plate subducts the other Oceanic crust – Continental crust Oceanic crust subducts the continental crust Continental – Continental crust Both plates DO NOT subduct and result in heavy folding

The Andes Mountains The Nazca plate crashed into South America This is a convergent boundary resulted in the South American landmass being crunched into a mountain range and a depression forming off the coast of the Pacific Ocean

The Himalayan Mountains The Himalayan mountains are an example a mountain range created through convergent boundary interactions. Between the Australian (Indian) plate and the Eurasian plate

Test Yourself Read Section 4.2 Answer Questions: 1-5 on pg. 77 Complete Chapter 4 Review on pages 78 and 79 Questions #1-14, Critical Thinking Questions 1-4