Meteorite Impact! (eBook)

Contents 
6 
Foreword 
10 
Part I 13
Chapter 1: The early history of Earth 15
Introduction 
16 
Geological change 
18 
Man on the Moon 
24 
Back to the beginning 
29 
Impact 
31 
The oldest rocks 
32 
Time to cool 
35 
Old crust in the Vredefort Dome 
37 
Rifting, oceans, volcanism 
38 
Mountains, fire and ice 
44 
The unique Bushveld magmatic event 
46 
Chapter 2: Chaos and 
49 
Introduction 
50 
Extinction or survival 
53 
Meteorite-impact catastrophes 
67 
Normal (background) versus mass extinctions 
72 
The Smoking gun! 
74 
Vredefort 
75 
A brief look at the impact record in the Solar System 
76 
How did impact science getstarted? 76
Craters on the Moon 82
From the Moon to the Earth-Moon system 82
The 
83 
The 
86 
What are the projectiles capable of causing an impact catastrophe? 
87 
Meteors and meteorites 
87 
Large asteroids and comets 89
What is an impact crater? 
90 
How can we identify impact structures? 
92 
Shock metamorphism 
97 
Chapter 3: The impact heritage of southern 
101 
Tswaing meteorite crater 
102 
Solving the riddle of the origin of Tswaing 103
The 
105 
What do we know about the landscape in the Tswaing area prior to the impact? 105
What would the catastrophe have been like? 106
Were there any witnesses of the catastrophic impact at Tswaing? 107
Does Tswaing have a twin? 
108 
South Africa's other giant impact 
109 
Our southern African neighbours 
111 
Testimony of earlier impact catastrophes 
113 
Traces of catastrophe in the Karoo? 
115 
Chapter 4: Vredefort: the largest and oldest impact structure in the World 
117 
The Vredefort Structure revealed 
118 
Getting to know the giant 
120 
Traversing the outer parts of the Vredefort Dome 
125 
The Geology of the Vredefort Dome 
130 
The unique rock formations and deformation in the Vredefort Dome 
134 
The findings of the early Vredefort gealogists 
138 
The second phase 
141 
Craters and breccias 144
Shock meta 
145 
The vredefort structure in the 1970s and 1980s 
148 
What do dead elephants in Leningrad have to do with the Vredefort Structure? 151
The third phase 
153 
Shocked zircon and a precise agefor the impact event 155
How big is 'big'? 157
Vredefort research in the 21st century 
159 
Vredefort 
161 
Chapter 5: The recent history of the Vredefort 
163 
Section 1: Travelling through time 
164 
Introduction 164
Stone Age Vredefort Dome 165
The Iron Age 168
Archaeological research on the Askoppies Late Iron Age site 170
Archaeology of the historical period on the dome 175
Section 2: Beyond the frontier history of the Vredefort Dome area 
179 
The geographic setting 181
Development of towns 183
Treading on territorial toes 185
Mineral resources 187
The Second Anglo-Boer War (1899–1902) 189
After the war 195
20th Century developmentand growth 196
Development of infrastructure 198
Development of tourism 199
Workers and forced removals 199
Section 3: Flora and fauna of the Vredefort dome 
201 
The Vredefort Dome plants (flora) in a geographical context 201
The composition of the flora 201
Which biome occurs on the VredefortDome? 203
Veld types on the Vredefort Dome 203
Factors that affect the vegetation 205
The habitats on the Vredefort Dome 207
The effect of geology on the vegetation of the Vredefort Dome 207
Recent changes in habitats on the Vredefort Dome 208
Woody vegetation in the Vredefort Dome 210
Fauna in the Vredefort Dome 210
Chapter 6: Frequently asked questions 215
Frequently asked questions about the Vredefort impact event 
216 
Where is the projectile responsible for the Vredefort impact? 216
Do we know from which direction the Vredefort bolide came? 216
Do we know how large the bolide was that caused the Vredefort catastrophe? 218
Could any life forms have perished in this catastrophe? 219
Would this impact have influenced further development of life? 219
Can there be other impact structures of the size of Vredefort, not yet discovered on Earth? 219
Major diamond, gold and platinum resources lie close to the Vredefort Dome. Why have no major ore deposits been found in the dome itself? 220
Is Vredefort truly unique? 221
Is the Cradle of Humankind related to the impact structure? 222
Chapter 7: What does the future hold for humankind? 225
What does the future hold for humankind? 
226 
Chapter 8: 
233 
Outlook 
234 
The 
236 
Part II 
241 
Tour guide through the Vredefort Dome 
242 
Stops 1–9: the core of the vredefort dome 
244 
Stop 1: Vredefort Dome World Heritage Site 
244 
Stop 2: Inlandsee pan and the centre of the 
246 
Stop 3: Ancient oceanic crust at Greenlands 247
Stop 4: 
249 
Stop 5: Steynskraal pelitic granulites — a thermal 
251 
Stop 6: 
252 
Stop 7: Pseudotachylitic breccia and gneisses in 
252 
Stop 8: Vredefort Granophyre and Bushman 
257 
Stop 9: Vredefort Granophyre and Dominion 
258 
Stops 10-22: 
262 
Stop 10: Rocks and metamorphism of the Central Rand Group (Witwatersrand Supergroup), 
262 
Stop 11: 
265 
Stop 12: Gold mining in the Venterskroon area 
266 
Stop 13: Shatter cones in the Booysens Formation, Rooderand 267
Stop 14: Amazon gold reef, Rooderand 270
Stop 15: Ventersdorp lavas, Askoppies Iron Age settlement and Anglo-Boer War sites on Tygerfontein farm 271
Stop 16: Stromatolites and cave in Transvaal rocks of the western collar 272
Stop 17: Schoemansdrift Bridge shatter cones 273
Stop 18: Dwarsberg (Steenkampsberg) view site 274
Stop 19: Rocks and metamorphism of the lower Witwatersrand Supergroup, Kommandonek Nature Reserve 274
Stop 20: Impact-induced fold and view site, Parson’s Rus 275
Stop 21: Coesite-stishovite-bearing quartzite, Kromellenboog Stream 276
Stop 22: Witwatersrand Supergroup quartzite, impact fault and Bobbejaanrant viewpoint, Smilin' Thru Resort 277
Acknowledgements 278
Bibliography 279
Glossary 288
Appendices 305
Appendix 1 
305 
Appendix 2 311
Appendix 3 
319 
Index 
324