The Visible Earths
01- Nazca,Cocos,Caribbean
02- Pre-Cambrian
03- Shields of the Earth
04- Shield Re-assembly
05- Volcanic Activity
06- Hinge Faults
07- Himalayas
08- Juan De Fuca, Gorda
09- Ring of Fire
10- Oceans Closed
11- Earthquake Waves
12- Mirror Plates
13- Interior
14- Continent Reflections
15- Earthquake Paths
16- Object in the interior
17- Magnetic Mirror
18- Full Expansion
19- Contraction
20- Shield Volcanoes
21- Valles Marineris
22- Entry Point of Mars
  The Gas Giants
23- The Gas Giants
24- Asteroids
25- Mercury
26- Venus' Crust
27- Gravity Anomalies
28- Free-Air Correction
29- Rudimentary America
30- Magma Oceans
31- Full Sequence & Notes

20 - Shield Volcanoes

Click here for enlarged diagram


The three extensional plates of the seabeds of Central America, having become an epicentre for increased earthquake and volcanic activity, continue to drive the overall pattern of the shield and plate movement. As this tectonic activity slows and eventually ceases, these fault lines and resulting areas of volcanic activity, come to rest at the positioning of the three large shield volcanoes of Tharsis, on the far side of Olympus Mons. The continuing spread of the Pacific seabeds becomes the Utopia Planitia of the Northern Plains. This movement can also be seen in the crustal magnetism.

The combined spreading of the seabeds and the reduction in the size of the sphere lead to an increasingly parallel crustal magnetic field, with warped and circular areas where the continents and the now shredded original shields are pushed together and swamped by new material from the mantle. These can be seen around Syrtis Major and on either side of Olympus Mons and Valles Marineris.

( The surface magnetic field, or crustal magnetism' in this section is based on the World Magnetic Declination Field and the Mars Crustal Magnetism chart from the Mars Global Surveyor )

Alan Lambert 2010