1.3 CHANGES DURING TRANSPORT

Question 1

WHAT IS THE ULTIMATE SEDIMENT SOURCE?

Answer 1

Mountains

Question 2

CHANGES IN TRANSPORT 1

Answer 2

e. g. alluvial fan; Badwater Death Valley
- initial sorting (alluvial fan) very poorly sorted
- through transport, ends up very well sorted e.g. beach

Question 3

CHANGES IN TRANSPORT 2

Answer 3

River/Lake sediments: increasing sorting, reducing angularity, reduction of less stable minerals due to ongoing chemical weathering.
Reduction of flow speed causes coarser materials to be left behind. Eventually only silt and clay sized material.
At mouth, flow speed further reduced - particular (bed) load deposited, and flocculation starts to remove suspended (clay) load.

Question 4

GRAIN SHAPE - WHAT IS ROUNDNESS & SPHERICITY?

Answer 4

Roundness = measure of the smoothness of grain surface; changes significantly through abrasion etc.

Sphericity = how closely grain shape approximates to sphere (w 3 orthogonal axes, x y x equal); changes much less, related to original properties of grain e.g. mineralogy

Question 5

What is evidence of transport by ice?

Answer 5

Faceted surface

Striations

Question 6

What is the evidence of transport by water on Mars?

Answer 6

Rounded pebbles in conglomerate outcrops