Level 2 Geography - Formation of Amazonia. Takapuna Grammar School

1. Formation of the
Amazon
Steps of Amazon Formation

2. Step one

3. Step one
• 500 Million years ago Gondwanaland split up into
sections, one of them was the precursor to modern
day Africa and South America. This break up
occurred due to strong convection currents in the
earths mantle. This rock was then subjected to
erosion, the eroded material was transported by
rivers, in which they accumulated and were
compressed under water into sandstone. An inland
lake formed which eventually drained into the
pacific.

4. Step Two

5. Step Two
• 90 Million years ago south america and Africa
separated from one another. As South America
shifted westward it collided with the Nazca plate
which was moving east. The collision pushed up the
softer sedimentary rock along the western
boundary to form fold mountains-the Andes. At the
same time land in the north and east
buckled, forming a basin.

6. Step Three

7. Step Three
• 2 Million years ago during the period named the
quaternary period the region experienced a cold
spell of ice age. This carved up the soft sedimentary
rock of the andes and caused much of it to be
reduced to sediment.
• Freeze thaw action and other denudations
processes have kept the height of the Andes to a
relatively constant height.
• The height of the Andes averages at 4000 m asl

8. Present Day
• Present This sediment was then transported by the
many tributaries of the Amazon, such as rio
Madeira. IN the upper reaches of the Andes steep
gradients mean that river flow is fast and erosion
extensive this creates deep v-shaped valleys. As the
sediment met the basin in the Andes foothills, river
flow was reduced and instead rivers began to
deposit their loads.

9. Present day
• Over time the rivers have built up the basin, making
it shallower and flatter. Today there is only a 100m
drop from the edge of the andes foothills to the
amazon mouth. Because of this the basin is liable to
flood seasonally, causing the build up of extensive
flood plains. Also the river meanders due to small
relief, causing widespread deposition across the
basin. Sediment tends to originate from the Andes
as the rock there is softer than the hard rock of the
Guyana and Brazilian plateau’s