シャドーイング練習: Rock Cycle | Igneous | Metamorphic | Sedimentary Rock - 動画で英語スピーキングを学ぶ
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115 文
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Rocks are all around us, and every rock you see used to be different.
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Over time rocks change.
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They break down, wear away, or even mount, but never disappear.
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How do rocks transform from this to this?
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Let's find out together in this episode all about the rock cycle.
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There are three types of rock found on Earth.
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Metamorphic, sedimentary, and igneous rock.
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We can classify each type of rock by how it was formed.
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Sometimes rocks form quickly, like when an erupting volcano spews molten rock into the air.
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And sometimes they change slowly, like when a rock is heated and compressed below
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Earth's surface for thousands or even millions of years.
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When you're looking at a rock, you're looking at history.
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Rocks may all seem the same at first, but they're all different and complex.
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The rock cycle shows how each type is formed in a different way, or how Earth's materials, driven by energy flow, change over time through melting,
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crystallization, weathering, erosion, and deformation.
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Within the Earth's crust and beneath the surface is molten rock
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or magma that can cool and solidify and turn into igneous rock.
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Let's take a look at Earth's layers to help us understand how this is possible.
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The Earth is made up of several layers that go all the way down to its core.
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The top layer of the Earth is slowly moving and shifting and is called the lithosphere.
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This layer consists of the Earth's crust and part of the upper mantle and makes up the tectonic plates, sometimes called lithospheric plates.
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These tectonic plates are being pushed together, pulled apart, or sliding past each other along surface faults.
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These movements are what create mountain ranges, seafloor trenches, and volcanoes.
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On the west coast of the United States, two plates are converging.
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The Pacific Plate is going underneath the North American Plate and begins to melt as it moves farther and farther down,
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eventually forming Mount Rainier and Mount St. Helens, which are active volcanoes.
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Old Oceanic Crust is constantly being recycled in the subduction zones.
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This is where Oceanic Crust, being more dense, is subducted or sinks below the continental crust where it melts and is recycled into the mantle.
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Volcanoes like this are a great place to find molten rock and igneous rock.
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You can see this action modeled here.
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At the bottom of this beaker, I have wax to represent magma under the crust.
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A layer of sand is resting on top to represent a thin layer of oceanic crust.
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As the magma rises, it cools and solidifies.
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When magma comes to the surface, it makes brand new rocks.
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Any new rock that has changed from molten to solid is an igneous rock.
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Igneous rocks make up about 90 % of Earth's crust, though you may not notice because they are covered up by other rocks, soil, or ocean.
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One common kind of igneous rock is granite.
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Behind me is enchanted rock.
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A massive 425 5 foot high, 1 .1 billion year old pink granite dome.
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Here is an exfoliated piece for us to get a closer look.
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Another type of igneous rock is this obsidian, which is smooth and glassy.
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Both of these rocks were made of molten rock, so why do they look so different?
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Depending on whether magma cools above or below
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Earth's surface will determine the type of igneous rock that is formed.
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When magma cools and solidifies beneath
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Earth's surface, it forms intrusive igneous rock.
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This granite is intrusive igneous rock.
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It has only been exposed by erosion or the removal of the surrounding rock.
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Intrusive rocks like this cool slowly so they have more time for larger mineral crystals to form,
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which is why granite looks coarse -grained and we can see the crystals even without a microscope.
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When magma erupts to the surface, we call it lava.
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After lava cools and solidifies, it becomes extrusive igneous rock.
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This obsidian is volcanic glass formed when lava cools rapidly with minimal crystal growth.
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If you're still here liking this video, let us know
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And hit that subscribe button so you never miss an episode.
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Once an igneous rock like granite is created, its journey isn't over.
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The rock begins to change through a process called weathering.
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Weathering wears away at exposed surfaces over time.
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It's the breakdown of rocks and minerals into smaller pieces or sediments.
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Brushing water in rivers can wear down sharp edges on rocks over time.
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High temperatures cause rock to expand, and falling temperatures cause rock to contract.
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As this cycle happens over and over again, the structure of the rock weakens.
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Eventually, the outer layers flake off in thin sheets, a process called exfoliation.
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That's what is happening here.
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You can see the curved cracks in peeling sheets.
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Looks a bit like a giant rock onion.
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All this sediment can be moved around or eroded by wind and water.
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Eventually, it will be deposited somewhere, joining sediment from other rocks at the bottom of a riverbed, lake, or ocean.
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Under the right circumstances, sediments can form into sedimentary rock.
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All the material in this sandstone once belonged to other rocks.
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These sedimentary rocks behind me were formed over 250 million years through the deposition of sediments in ancient seas and rivers,
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creating layers of red shale, sandstone, and gypsum.
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Rocks like these are formed when sediments undergo lithification.
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Before lithification can occur, we need sediments.
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So I'm going to create some candy sediments.
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This is taking a long time, so let's speed it up.
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That's better.
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The first step to lithification is called deposition.
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This is when sediment is deposited in a new location and it spreads out to form a layer.
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As more and more layers are created, the layers underneath them become pressed together.
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This is called compaction.
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Minerals settle between the sediment particles which makes everything stick together.
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This is called cementation, like cement.
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This is now our candy sedimentary rock.
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You can see the layers we started with the white and ended with the green.
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With enough heat or pressure, a metamorphic rock can be formed from any other type of rock,
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igneous, sedimentary, or even other metamorphic rocks.
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All of the minerals in the original rock recrystallize without having to melt down back into molten rock.
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The new metamorphic rocks are typically harder, more compact, and more resistant to weathering.
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Metamorphic means it's changed.
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We can create metamorphic rock with our sedimentary candy rock by adding heat and pressure.
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First, I'm going to use an old hairdryer to heat things up.
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Now, squishing action.
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Pressure!
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Squish!
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Pressure!
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Our sedimentary rock is now a metamorphic rock.
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These pink rock islands jutting up through the limestone are metamorphic rocks called valley spring gneiss.
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Intense heat and pressure applied to the original rocks over millions of years formed gneiss.
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The original rocks were sedimentary and igneous, likely granite.
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Rocks really never go away.
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They're changed and reused over time.
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This metamorphic rock can be heated up until it becomes like liquid lava.
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Once it cools, it's now an igneous rock.
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Back to the beginning.
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There are many pathways through the rock cycle.
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Metamorphic rocks and sedimentary rocks can become igneous rocks when they're melted and then cooled.
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Igneous rocks and sedimentary rocks can become metamorphic rocks when they're exposed to high heat and pressure.
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Igneous and metamorphic rocks can become sedimentary rocks if they're broken apart into sediments and go through lithification.
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So the next time you spot an interesting rock, see if you can tell.
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Is it sedimentary, igneous, or metamorphic?
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And if you want to learn more science you can check out this video next.
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Pressure!
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Squish!
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Pressure!
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このレッスンの語彙とスピーキングのポイント
繰り返し出てくる語は次のとおりです：rock, igneous, metamorphic, sedimentary, layer。 この動画には、シャドーイング用の文が115文、単語が1278語あります。 音声の長さは9:01です。 話す速さは1分あたり約142語で安定しており、シャドーイングしやすいペースです。 英語の頻出3,000語に含まれる単語は74%だけなので、語彙は難しめです。
この動画の重要語彙
動画に出てくる覚えておきたい単語15語を、発音と意味つきで紹介します。
| 単語 | 発音 | 意味 |
|---|---|---|
| layer 名詞 | /ˈleɪ̯ɚ/ | 層, 膜 |
| melt 動詞 | /mɛlt/ | 溶ける, 溶かす |
| granite 名詞 | /ˈɡɹæn.ɪt/ | 花崗岩 |
| mineral 名詞 | /ˈmɪn.ə.ɹəl/ | 鉱物 |
| volcano 名詞 | /vɑlˈkeɪ.noʊ/ | 火山 |
| lava 名詞 | /ˈlɑvə/ | 溶岩 |
| crystal 名詞 | /ˈkɹɪstəl/ | 結晶 |
| candy 名詞 | /ˈkæn.di/ | キャンデー, キャンディ |
| expose 動詞 | /ɪkˈspoʊz/ | 晒す, 暴く |
| thin 形容詞 | /ˈθɪn/ | 薄い, 細い |
| sheet 名詞 | /ʃit/ | 枚, シート |
| deposit 名詞 | /dɪˈpɑ.zɪt/ | 堆積物 |
| erosion 名詞 | /ɪˈɹəʊʒən/ | 浸食 |
| mantle 名詞 | /ˈmæn.təl/ | マント, マントル |
| sandstone 名詞 | /ˈsændˌstoʊn/ | 砂岩 |
動画に出てくる句動詞
| 単語 | 意味 |
|---|---|
| check out 動詞 | 試験する, 検査する |
| find out 動詞 | 見出す, 調べる |
| go away 動詞 | 去る, 出る |
| wear away 動詞 | 擦り減る, 擦り減らす |
この動画の文法
話し手がよく使っている文型を、動画の実際の表現とともに紹介します。
| 文型 | 動画での表現 |
|---|---|
| 受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる | was formed · is heated · is formed |
| 関係詞節 who / which + 節 — 人や物について情報を加える | Helens, which are · obsidian, which is · particles which makes |
| 現在完了形 have/has + 過去分詞 — 過去の出来事が今も関係している | has changed · has only been exposed |
注意したい発音
話し手はthey're, you're, I'mなど、短縮形や弱形を11回使っています。聞こえたとおりの短い形で発音しましょう。
- 「th」の音: thin /ˈθɪn/, beneath /bɪˈniːθ/, underneath /ˌʌndɚˈniθ/, smooth /smuːð/, pathway /ˈpæθˌweɪ/
- 「sh」と「zh」の音: sheet /ʃit/, erosion /ɪˈɹəʊʒən/, deposition /ˌdɛp.əˈzɪʃ.ən/, sharp /ʃɑɹp/, brush /bɹʌʃ/
- 長い単語（アクセントの位置に注意）: deposition /ˌdɛp.əˈzɪʃ.ən/, metamorphic /ˌmɛt.əˈmɔɹ.fɪk/, sedimentary /ˌsɛd.əˈmɛn.tə.ɹi/, lithification /ˌlɪθɪfɪˈkeɪʃən/, solidify /səˈlɪdɪˌfaɪ/
日本語話者が苦手な音：
- /r/ と /l/ の区別 — /l/ は舌先を歯茎につけ、/r/ はどこにもつけない: mineral /ˈmɪn.ə.ɹəl/, crystal /ˈkɹɪstəl/, removal /ɹɪˈmuː.vəl/, rapidly /ˈɹæpɪdli/, particle /ˈpɑɹtək(ə)l/
- /v/ — /b/ にならないように、上の歯を下唇に当てる: volcano /vɑlˈkeɪ.noʊ/, lava /ˈlɑvə/, removal /ɹɪˈmuː.vəl/, curve /kɚv/, volcanic /vɔlˈkænɪk/
- /f/ — 「フ」ではなく、上の歯と下唇で出す: transform /tɹænsˈfɔɹm/, metamorphic /ˌmɛt.əˈmɔɹ.fɪk/, lithification /ˌlɪθɪfɪˈkeɪʃən/, solidify /səˈlɪdɪˌfaɪ/, classify /ˈklæs.əˌfaɪ/
この動画での練習方法
- まず声を出さずに動画を最後まで聞き、知らない単語をメモします。
- 通常の速度で一文ずつシャドーイングし、話し手のリズムに合うまで繰り返します。
- 自分の声を録音して元の音声と比べます。layer, melt, graniteなどの単語に特に注意しましょう。
シャドーイングとは？英語上達に効果的な理由
シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。