1 / 9

Plate boundaries are marked in several ways:

Plate boundaries are marked in several ways: . Names of the plates: . (Lowrie, 1997) Arrows indicate relative velocities (mm/yr) from NUVEL-1 model of DeMets et al., 1990. Types of plate boundaries: . Assumptions of Plate Tectonics.

andrew
Download Presentation

Plate boundaries are marked in several ways:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Plate boundaries are marked in several ways:

  2. Names of the plates: (Lowrie, 1997) Arrows indicate relative velocities (mm/yr) from NUVEL-1 model of DeMets et al., 1990

  3. Types of plate boundaries:

  4. Assumptions of Plate Tectonics • The generation of new plate material occurs by seafloor spreading; that is, new oceanic lithosphere is generated along the active mid-ocean ridges. • The new oceanic lithosphere, once created, forms part of a rigid plate; this plate may or may not include continental material. • The Earth’s sruface are remains constant; therefore, seafloor spreading must be balanced by consumption of plate elsewhere. • The lithospheric plates are capable of transmitting stresses over great horizontal distances without buckling; in other words, the relative motion between plates is taken up only along plate boundaries.

  5. Plate motions can be determined in several ways. The traditional way is using marine magnetic anomalies:

  6. Magnetic anomalies allow the identification of isochrons in the worlds oceans.

  7. Very Long Baseline Interferometry (VLBI) VLBI measures the time difference between the arrival at the Earth of a radio signals emitted by quasars. The time difference between arrivals at two satellites is proportional to the distance between the two satellites and the direction of the source. These satellites may be separated by some 10,000 km. Using large numbers of time difference measurements from many quasars observed with a global network of antennas, VLBI determines the inertial reference frame defined by the quasars and simultaneously the precise positions of the antennas. Because the time difference measurements are precise to a few picoseconds, VLBI determines the relative positions of the antennas to a few millimeters and the quasar positions to fractions of a milliarcsecond. Since the antennas are fixed to the Earth, their locations track the instantaneous orientation of the Earth in the inertial reference frame.

  8. Satellite and Lunar Laser ranging (SLR & LLR)  SLR targets are satellites equipped with corner cubes or retro-reflectors. Currently, the global SLR network tracks over forty such satellites. The observable is the round-trip pulse time-of-flight to the satellite. SLR systems are equipped with short-pulse laser transmitters that can range to orbiting satellites. Lunar Laser Ranging (LLR) systems can range to retro-reflectors located on the moon.

  9. Global positioning system (GPS) There are  24 GPS satellites currently in circular orbits some  20,200 kilometers above the Earth.  At any one time in most places six  can be "seen" by GPS receivers that  get and process signals.   GPS receivers  calculate current position (latitude, longitude, altitude) with varying degrees of precision.   There are over 200 permanent GPS receivers located world wide.  These provide data for modeling plate motions on yearly time scales.

More Related